Search

This review highlights the use of DACH as a versatile ligand in catalytic asymmetric transformations providing mechanistic rationales and relevant comments presented in chronological order for each of the 21 reaction types with references up to December 25, 2023. Intended to be as practically comprehensive as possible, this review assembles useful examples of using DACH as a ligand in organocatalytic or as metal complexes in asymmetric transformations. The resulting enantiomerically enriched, if not pure, chiral non-racemic small molecules are of great utility as value added intermediates in the total synthesis of natural products, in the design and synthesis of medicinally important compounds, and in other areas in organic and bioorganic chemistry where chirality plays a role. The graphic image depicts Spartacus with his arms folded in the same sense of chirality as (R , R)-DACH. 1 Introduction 2 DACH: A Brief Historical Narrative 3 Catalytic Asymmetric Hydrogenation of Alkenes 4 Catalytic Asymmetric Dihydroxylation of Alkenes 5 Catalytic Asymmetric Sulfoxidation and Sulfimidation 6 Catalytic Asymmetric 1,4-Conjugate Addition 6.1 Using Jacobsen's DACH Metal–salen Complexes as Catalysts 6.2 Using Takemoto's Bifunctional H-Bonding DACH Thiourea Organocatalyst 6.3 Using DACH Ni(II) Complexes as Catalysts 6.4 Using DACH H-Bonding Catalysis 7 Catalytic Asymmetric Epoxidation of Alkenes 8 Catalytic Asymmetric Claisen Rearrangement 9 Catalytic Asymmetric 1,2-Nucleophilic Addition to Carbonyl Compounds 9.1 Catalytic Asymmetric Addition of Dialkylzinc to Aldehydes and Ketones 9.2 Catalytic Asymmetric Alkynylation of Aldehydes and Ketones 9.3 Catalytic Asymmetric Addition of Cyanide to Aldehydes and Ketones 10 Catalytic Asymmetric Allylic Alkylation 11 Catalytic Asymmetric Cyclopropanation of Alkenes 12 Catalytic Asymmetric Cycloaddition Reactions 13 Catalytic Asymmetric Aziridination of Alkenes 14 Catalytic Asymmetric Hydrogenation of Prochiral Ketones and Imines 15 Catalytic Asymmetric Aldol Reactions 16 Catalytic Asymmetric Opening of Small Ring Systems 16.1 Desymmetrization of meso -Epoxides and meso -Aziridines 16.2 Kinetic Resolution of Racemic Epoxides 16.3 Enantioselective Addition of CO2 to Epoxides 16.4 Enantioselective Ring Opening of Oxetanes 17 Catalytic Asymmetric Strecker Reactions 18 Catalytic Asymmetric Mannich Reactions 19 Catalytic Asymmetric Henry and Aza-Henry Reactions 20 Catalytic Asymmetric Morita–Baylis–Hillman and Rauhut–Currier Reactions 21 Catalytic Asymmetric Petasis Reactions 22 Organocatalytic Asymmetric Cascade Reactions 23 Miscellaneous Catalytic Reactions 24 Conclusion and Outlook 25 DACH Catalysts and Ligands List [ABSTRACT FROM AUTHOR]

This study investigates the application of quantum mechanical (QM) and multiscale computational methods in understanding the reaction mechanisms and kinetics of SN2 reactions involving methyl iodide with NH2OH and NH2O−, as well as the Claisen rearrangement of 8-(vinyloxy)dec-9-enoate. Our aim is to evaluate the accuracy and effectiveness of these methods in predicting experimental outcomes for these organic reactions. We achieve this by employing QM-only calculations and several hybrids of QM and molecular mechanics (MM) methods, namely QM/MM, QM1/QM2, and QM1/QM2/MM methodologies. For the SN2 reactions, our results demonstrate the importance of explicitly including solvent effects in the calculations to accurately reproduce the transition state geometry and energetics. The multiscale methods, particularly QM/MM and QM1/QM2, show promising performance in predicting activation energies. Moreover, we observe that the size of the MM active region significantly affects the accuracy of calculated activation energies, highlighting the need for careful consideration during the setup of multiscale calculations. In the case of the Claisen rearrangement, both QM-only and multiscale methods successfully reproduce the proposed reaction mechanism. However, the activation free energies calculated using a continuum solvation model, based on single-point calculations of QM-only structures, fail to account for solvent effects. On the other hand, multiscale methods more accurately capture the impact of solvents on activation free energies, with systematic error correction enhancing the accuracy of the results. Furthermore, we introduce a Python code for setting up multiscale calculations with ORCA, which is available on GitHub at https://github.com/iranimehdi/pdbtoORCA. [ABSTRACT FROM AUTHOR]

We report a synthetic approach to π‐expanded [6]helicenes incorporating tropone and azocine units in combination with a 5‐membered ring, which exhibit intriguing structural, electronic, and chiroptical properties. The regioselective Beckmann rearrangement allows the isolation of helical scaffolds containing 8‐membered lactam, azocine, and amine units. As shown by X‐ray crystallographic analysis, the incorporation of tropone or azocine units leads to highly distorted [6]helicene moieties, with distinct packing motifs in the solid state. The compounds exhibit promising optoelectronic properties with considerable photoluminescence quantum yields and tunable emission wavelengths depending on the relative position of the nitrogen center within the polycyclic framework. Separation of the enantiomers by chiral high‐performance liquid chromatography (HPLC) allowed characterization of their chiroptical properties by circular dichroism (CD) and circularly polarized luminescence (CPL) spectroscopy. The azocine compounds feature manifold redox chemistry, allowing for the characterization of the corresponding radical anions and cations as well as the dications and dianions, with near‐infrared (NIR) absorption bands extending beyond 3000 nm. Detailed theoretical studies provided insights into the aromaticity evolution upon reduction and oxidation, suggesting that the steric strain prevents the azocine unit from undergoing aromatization, while the indene moiety dominates the observed redox chemistry. [ABSTRACT FROM AUTHOR]

The cascade reaction of ynamides with propargyl thiols by Au(I) catalysis involving regioselective hydrothiolation, thio‐Claisen rearrangement, and cycloisomerization to generate 2‐aminothiophenes in a one‐pot manner is described. In this reaction, the selection of reaction temperature is crucial, with the initial step, namely hydrothiolation, conducted at a low temperature (40 °C), followed by the subsequent reaction requiring an increase in temperature (>110 °C). Furthermore, it was revealed that multi‐substituted anilines could be synthesized from the resulting 2‐aminothiophenes. [ABSTRACT FROM AUTHOR]

Donor-acceptor Stenhouse adducts (DASAs) are molecular photoswitches spurring wide interest because of their dynamic photophysical properties, complex photoswitching mechanism, and diverse applications. Despite breakthroughs in modularity for the donor, acceptor, and triene compartments, the backbone heteroatom remains static due to synthetic challenges. We provide a predictive tool and sought-after strategy to vary the heteroatom, introduce amino DASA photoswitches, and analyze backbone heteroatom effects on photophysical properties. Amino DASA synthesis is enabled by aza-Piancatelli rearrangements on pyrrole substrates, imparting an aromaticity-breaking rearrangement that capitalizes on nitrogen's additional bonding orbital and the inductive properties of sulfonyl groups. Amino DASA structure is confirmed by single crystal X-ray diffraction, the photochromic properties are characterized, and the photoswitch isomerization is investigated. Overall, the discovered pyrrole rearrangement enables the study of the DASA backbone heteroatom compartment and furthers our insight into the structure-property relationship of this complex photoswitch. It is a synthetic challenge to modulate the backbone heteroatom of donor-acceptor Stenhouse adducts limiting their photoswitchable properties. Here, the authors address the challenge with the introduction of an amino functionality into the photoswtich backbone and investigate their resulting photoswitch isomerization. [ABSTRACT FROM AUTHOR]

Tandem aromatic rearrangements represent a potent strategy for modulating the regioselectivity of a rearrangement process. In this article, we disclose two novel tandem aromatic rearrangements triggered by sulfonium [5,5]-rearrangement recently developed in our laboratory. Specifically, the [5,5]-rearrangement of aryl sulfoxides with allyl nitriles, followed by [3,3]-Cope rearrangement, forges a seamless tandem [5,5]-/[3,3]-rearrangement cascade, affording ortho -functionalized aryl sulfides. The other tandem process involves [5,5]-rearrangement of aryl sulfoxides with allyl nitriles, followed by nucleophilic addition/DDQ-oxidation-induced [3,3]-Cope rearrangement, eventually yielding meta -functionalized aryl sulfides. Both consecutive rearrangements enrich the repertoire of tandem aromatic rearrangement methodologies. [ABSTRACT FROM AUTHOR]

A de novo asymmetric strategy for the synthesis of d‐bradyrhizose diastereomers from an achiral ketoenolester precursor is described. Key transformations used in the stereodivergent approach include two Noyori asymmetric reductions, an Achmatowicz rearrangement, diastereoselective alkene oxidations, and the first example of a palladium(0)‐catalyzed glycosylation of a vinylogous pyranone. The isomeric composition of the bicyclic reducing sugars obtained was analyzed and their behaviour was compared to the natural product, revealing key stereocentres that impact the overall distribution. [ABSTRACT FROM AUTHOR]

We here reported a highly stereoselective method for the synthesis of polysubstituted conjugated dienes from α‐aryl α‐diazo alkynyl ketones and pyrazole‐substituted unsymmetric aminals under mild conditions, which was promoted by photo‐irridation and involved with 1,6‐dipolar intermediate and quadruple sigmatropic rearrangements, was successfully developed. In this transformation, the cleavage of four bonds and the recombination of five bonds were implemented in one operational step. This protocol provided a modular tool for constructing dienes from amines, pyrazoles and α‐alkynyl‐α‐diazoketones in one‐pot manner. The results of mechanistic investigation indicated that the plausible reaction path underwent the 1,6‐sigmatropic rearrangement instead of the 1,5‐sigmatropic rearrangement. [ABSTRACT FROM AUTHOR]

A de novo asymmetric strategy for the synthesis of d‐bradyrhizose diastereomers from an achiral ketoenolester precursor is described. Key transformations used in the stereodivergent approach include two Noyori asymmetric reductions, an Achmatowicz rearrangement, diastereoselective alkene oxidations, and the first example of a palladium(0)‐catalyzed glycosylation of a vinylogous pyranone. The isomeric composition of the bicyclic reducing sugars obtained was analyzed and their behaviour was compared to the natural product, revealing key stereocentres that impact the overall distribution. [ABSTRACT FROM AUTHOR]

Despite the significance of chiral allene skeletons in catalysis, organic synthesis and medicinal chemistry et al. there is a scarcity of reports on axially chiral allenyl phosphorus compounds. Here, we disclosed an efficient and straightforward cascade reaction between ethynyl ketones and phosphine oxides, resulting in a broad array of trisubstituted allenes incorporating a phosphorus moiety in high yields with excellent stereoselectivities facilitated by peptide‐mimic phosphonium salt (PPS) catalysis, Additionally, comprehensive series of mechanistic experiments have been conducted to elucidate that this cascade reaction proceeds via an asymmetric Pudovik addition reaction followed by a subsequent phospha‐Brook rearrangement that occurs concomitantly with kinetic resolution, representing a stereospecific rearrangement and protonation process facilitating central‐to‐axial chirality transfer in a cascade manner. We anticipate that our research will pave the way for a promising exploration of novel stereo‐induction pattern in the Pudovik addition/phospha‐Brook rearrangement cascade reaction. [ABSTRACT FROM AUTHOR]

Complex networks are pervasive in various fields such as chemistry, biology, and sociology. In chemistry, first-order reaction networks are represented by a set of firstorder differential equations, which can be constructed from the underlying energy landscape. However, as the number of nodes increases, it becomes more challenging to understand complex kinetics across different timescales. Hence, how to construct an interpretable, coarse-graining scheme that preserves the underlying timescales of overall reactions is of crucial importance. Here, we develop a scheme to capture the underlying hierarchical subsets of nodes, and a series of coarse-grained (reduceddimensional) rate equations between the subsets as a function of time resolution from the original reaction network. Each of the coarse-grained representations guarantees to preserve the underlying slow characteristic timescales in the original network. The crux is the construction of a lumping scheme incorporating a similarity measure in deciphering the underlying timescale hierarchy, which does not rely on the assumption of equilibrium. As an illustrative example, we apply the scheme to four-state Markovian models and Claisen rearrangement of allyl vinyl ether (AVE), and demonstrate that the reduced-dimensional representation accurately reproduces not only the slowest but also the faster timescales of overall reactions although other reduction schemes based on equilibrium assumption well reproduce the slowest timescale but fail to reproduce the second-to-fourth slowest timescales with the same accuracy. Our scheme can be applied not only to the reaction networks but also to networks in other fields, which helps us encompass their hierarchical structures of the complex kinetics over timescales. [ABSTRACT FROM AUTHOR]

Iridium-catalyzed dearomative allylation/acyl transfer rearrangement has been developed using easily available 2-pyridinyl benzoates and vinyl ethylene carbonate. This protocol enabled the expedient synthesis of a variety of chiral N-substituted 2-pyridones in good to high yields with excellent enantioselectivity. It has the advantages of high atom economy, wide substrate scope, gram-scale synthesis, and versatile synthetic transformations. [ABSTRACT FROM AUTHOR]

In the last several years, there has been a surge in the development of machine learning potential (MLP) models for describing molecular systems. We are interested in a particular area of this field -- the training of system-specific MLPs for reactive systems -- with the goal of using these MLPs to accelerate free energy simulations of chemical and enzyme reactions. To help new members in our labs become familiar with the basic techniques, we have put together a self-guided Colab tutorial (https://cc-ats.github.io/mlp_tutorial/), which we expect to be also useful to other young researchers in the community. Our tutorial begins with the introduction of simple feedforward neural network (FNN) and kernel-based (using Gaussian process regression, GPR) models by fitting the two-dimensional Müller-Brown potential. Subsequently, two simple descriptors are presented for extracting features of molecular systems: symmetry functions (including the ANI variant) and embedding neural networks (such as DeepPot-SE). Lastly, these features will be fed into FNN and GPR models to reproduce the energies and forces for the molecular configurations in a Claisen rearrangement reaction. [ABSTRACT FROM AUTHOR]

This document provides a detailed account of the synthesis of three calyciphylline A-type alkaloids: (+)-daphlongamine E, (+)-calyciphylline R, and (-)-10-deoxydaphnipaxianine A. The authors describe the synthetic efforts and challenges faced in achieving these compounds, as well as the unique protecting group used in the synthesis of (-)-10-deoxydaphnipaxianine A. The synthesized compounds were characterized and compared to their natural counterparts. The document is technical and specific to the field of organic chemistry, making it suitable for researchers in the field. [Extracted from the article]

The aromatic Cope rearrangement is an elusive transformation that has been the subject of a limited number of investigations compared to those seemingly close analogues, namely the Cope and aromatic Claisen rearrangement. Herein we report our investigations inspired by moderate success observed in the course of pioneering works. By careful experimental and theoretical investigations, we demonstrate that key substitutions on 1,5‐hexadiene scaffold allow fruitful transformations. Especially, efficient functionalisation of the heteroaromatic rings results from the aromatic Cope rearrangement, while highly stereoselective interrupted aromatic Cope rearrangements highlight the formation of chiral compounds through a dearomative process. [ABSTRACT FROM AUTHOR]

An efficient stereoselective synthesis of cis-2,6-disubstituted tetrahydropyrans 14a–c has been achieved via gold-catalyzed Meyer–Schuster rearrangement/hydration/oxa-Michael addition sequence from bis-propargylic alcohols 13a–c. The reaction of 13a proceeds via 2,6-disubstituted tetrahydropyran 14′a as an intermediate. [ABSTRACT FROM AUTHOR]

A convenient and operationally trivial protocol to access synthetically versatile vinylboronates through CuI catalyzed hydroboration and carboboration of alkynes utilizing bis(pinacolato)diboron (B2pin2) as the boron precursor in a 1, 10‐phenanthroline (phen) ligand environment is reported. This is a highly efficient and practical method for the synthesis of regio‐ and stereoselective (E)‐β‐vinylboronates from simple aromatic and aliphatic alkynes. These organoboron compounds have further been utilized for the synthesis of allyl‐vinyl ethers, which are potential starting materials for the Claisen rearrangement via an improved CuII mediated coupling of allyl alcohols and vinylboronates. The vinylboronates were also subjected to Suzuki‐Miyaura cross coupling reaction, allowing access to the corresponding tri‐ and tetra‐substituted alkenes with good isolated yields. [ABSTRACT FROM AUTHOR]

A production technique with the high yield and environmentally friendly process need be developed for ε-Caprolactam (CPL) in the chemical industry. This technology is highly desired to design and synthesize high-performance catalysts for liquid phase Beckmann rearrangement of cyclohexanone oxime (CHO) to CPL. In this work, 3-methyl-1-(propyl-4-sulfonyl) imidazolium methanesulfonate ([PHSO3MIM][MSA]) with highly efficient and excellent yield is synthesized successfully. When the optimum molar ratio of ZnCl2 over [PHSO3MIM][MSA] was 0.02, it exhibits the high selectivity &#(94%) of CPL at 90 °C for 1 h. Interestingly, Fourier-transform infrared (FT-IR) investigations show that the functional Brønsted-Lewis acidic types of ionic liquids (ILs) are formed by the uniformly distributed ZnCl2 and [PHSO3MIM][MSA]. In addition, the hydrogen bond (H-bond) is formed between CHO and ILs. After ten reaction cycles, no significant structure changes are observed in the recovered [PHSO3MIM][MSA]·ZnCl2. The solubilities of ILs are predicted by using COSMO-RS model, the results show that [PHSO3MIM][MSA] is a promising candidate for the liquid phase Beckmann rearrang;ement of CHO into CPL. Finally, a theoretical model of the H-bond interactions between ILs and CHO is further confirmed to support the advance of reaction mechanism. A feasible way is provided for the CPL production technique in the liquid phase Beckmann rearrangement reaction. [ABSTRACT FROM AUTHOR]

The 1,2‐rearrangement reaction is one of the most important approaches to construct carbon‐carbon bonds in organic synthesis. However, the development of catalytic asymmetric 1,2‐rearrangements is still far from mature and often suffers from problems such as complex substrates, single product structure, and lack of synthetic application. Multicomponent reaction has been recognized as a robust tool for the synthesis of diverse and tunable products from readily available starting material. Conceptionally and practically, the development of multicomponent asymmetric 1,2‐rearrangements is highly desirable. In this regard, we report herein a three‐component benzilic acid‐type rearrangement of 2,3‐diketoesters, aromatic amines and aldehydes for the asymmetric construction of synthetically challenging pyrrolinones bearing aza‐quaternary stereocenters. To the best of our knowledge, this reaction represents the first example of organocatalyzed multicomponent asymmetric 1,2‐rearrangements. [ABSTRACT FROM AUTHOR]

It was found for the first time that 2,3-dialkyl-substituted gem-dibromocyclopropanes react with a solution of the aluminum carbenoid Me2AlCH2I in CH2Cl2 to form substituted bromoalkenes in a good yield. The reaction is sensitive both to the nature of the organoaluminum Lewis acid and to the substitution in gem-dibromocyclopropane. A mechanism of the cyclopropyl–allyl rearrangement was proposed. The free activation energies of the cyclopropyl–allyl rearrangement were calculated by the B3LYP/6-31G(d) method for a number of gem-dibromocyclopropanes and aluminum-containing Lewis acids. [ABSTRACT FROM AUTHOR]

The degradation behavior of mandestrobin (1) was investigated in aerobic aquatic water--sediment systems exposed to continuous artificial sunlight (λ>290 nm). [14C]mandestrobin uniformly labeled at the phenoxy or benzyl ring was individually applied to the overlying water of the system at a rate equivalent to 262.5 g a.i./ha. The transformation of 1 was mainly proceeded via photoinduced bond cleavage at the benzyl phenyl ether and the subsequent rearrangement reaction. Interestingly, some of the photodegradates and microbial metabolites of 1 observed in the aquatic photodegradation and water--sediment (dark) studies, respectively, were never detected. Furthermore, the observed photoproducts were less formed and were steadily degraded or metabolized to carbon dioxide or strongly adsorbed to bottom sediment. The fate of 1 and its degradates in illuminated water--sediment systems was considered to reflect realistic conditions more precisely, as it accounts for various effects attributed to sunlight. [ABSTRACT FROM AUTHOR]

In this study, the total synthesis of osajin, scandenone and their analogues have been accomplished. The key synthetic steps include aldol/intramolecular iodoetherification/elimination sequence reactions and a Suzuki coupling reaction to assemble the tricyclic core, chemoselective propargylation and Claisen rearrangement reactions to obtain natural compounds. In addition, we also designed and synthesized twenty-five natural product analogues. All synthetic compounds were screened for anti-inflammatory activity against tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Collectively, Compound 39e and 39d were considered as promising lead compounds for further development. [ABSTRACT FROM AUTHOR]

The accomplishment of self‐healing polybutadienes (PB) is decisive for multitude of aerospace applications. We here present the first‐time report on a self‐healing PB derived from a blend of allyloxy end functionalized PB elicited through intramolecular thermally activated sigmatropic Claisen rearrangement coupled with stratified hydrogen bonding for use in polymer bonded explosives (PBX). Heteronuclear Single Quantum Correlation (HSQC), Heteronuclear Multiple Bond Coherence (HMBC), Total Correlation Spectroscopy (TOCSY) and Fourier Transform Infrared spectroscopy (FTIR) Spectroscopy were utilized to confirm the mechanistic aspects of the rearrangement for the proposed application. The mechanism of self‐healing is further elucidated using density functional theory (DFT) computations and confirmed through Raman spectroscopy. The biphasic polymer network architecture is disclosed through two glass transitions at −54 °C and 15–25 °C, as confirmed by Dynamic Mechanical Analysis (DMA) and Atomic Force Microscopy (AFM). The polymer exhibited healing efficiency of 85 % suitable for adhesive or coating applications. Self‐healing in bonding formulations of insensitive polymer bonded explosives was also expedited which exhibited a healing efficiency of 49–54 %. [ABSTRACT FROM AUTHOR]

Herein, we report an unprecedented skeletal rearrangement reaction of tetrahydro‐β‐carbolines enabled by copper‐catalyzed single‐electron oxidative oxygenation, in which H2O and O2 act as oxygen sources to generate a unique 2‐hydroxyl‐3‐peroxide indoline intermediate. The synthetic reactivity of 2‐hydroxyl‐3‐peroxide indoline species was demonstrated by a unique multi‐step bond cleavage and formation cascade. Using a readily available copper catalyst under open‐air conditions, highly important yet synthetically difficult spiro[pyrrolidone‐(3,1‐benzoxazine)] products were obtained in a single operation. The synthetic utility of this methodology is demonstrated by the efficient synthesis of the natural products donaxanine and chimonamidine, as well as the 3‐hydroxyl‐pyrroloindoline scaffold, in just one or two steps. [ABSTRACT FROM AUTHOR]

A high-temperature continuous flow protocol is reported for the intensified synthesis of an important industrial raw material via aromatic Claisen rearrangement of the corresponding diallyl ether precursor. The process takes advantage of solvent-free conditions, thereby maximizing productivity whilst reducing cost and environmental impact. By precise control over reaction temperature and residence times, a high-yielding and selective synthesis is achieved that ensures improved safety and scalability of the exothermic transformation compared with earlier batch methodologies. [ABSTRACT FROM AUTHOR]

In this report, we describe the combination of [5,5]‐rearrangement‐triggered dearomatization recently developed in our laboratory with an intramolecular formal [2+2]‐cycloaddition for constructing an intriguing polysubstituted tricyclo[4.2.1.03,8]nonane derivatives. The synthesis features the use of simple and readily available three distinct starting materials including aryl sulfoxides, allyl nitriles, and certain nucleophiles or dienes which directly enriches the diversity of target molecules. This study provides an entirely new protocol for the synthesis of cyclobutane‐centered tricyclic caged skeleton. [ABSTRACT FROM AUTHOR]

Plasmonic-heat generated from the solar irradiation of gold nanoparticles is used as the thermal energy source for the Claisen rearrangement of allyl phenyl ether to 2-allylphenol, which is conventionally performed with electrical heating at 250 °C. The use of a closed reactor enables the physical separation of the reactants from the source of plasmonic-heat, thereby preventing the interference of the hot-charge carriers in the plasmon-driven Claisen rearrangement. In this way, the sole effect of plasmonic-heat in driving a high temperature organic transformation is demonstrated. Our study reveals the prospects of plasmonic nanostructures in conducting energy intensive chemical synthesis in a sustainable fashion. [ABSTRACT FROM AUTHOR]

Idose-type glycosides have numerous biological activities and have been widely used as anticoagulant drugs and anti-infection drugs. Thioglycosides have enhanced stability for acid-mediated or enzymatic hydrolysis, and have a wide range of applications in glycobiology and drug development. Herein, we describe an efficient method for site-selective and stereoselective synthesis of potential bioactive 2-amino-2-deoxy-1,3-dithioidoglycosides via organocatalysis sequential C3-Ferrier rearrangement and Michael addition of 3-O-acetyl-2-nitrogalactals. Both stepwise and one-pot protocols were carried out and work well. This unique thio-glycosylation protocol highlighted the various advantages, including (i) mild reaction conditions; (ii) excellent site-selectivity and stereoselectivity, good to excellent yields; (iii) broad substrate scopes; (iv) being atom-economic and environmentally friendly; (v) the reactions can be scaled up. [ABSTRACT FROM AUTHOR]

Acetylene terminated polymers are gaining interest due to the need for easily processable thermally stable networks. The Metal Organic Frameworks (MOFs)—aluminum fumarate (Al_FA_A) and copper fumarate (Cu_FA_A) MOFs were synthesized and blended with bispropargyl ether (bis (4-propargyloxyphenyl) sulfone—SPE). The (SPE + 1% MOFs) blends were characterized and thermally polymerized to give P(SPE + MOFs). The synthesized materials were characterized using FTIR, DSC, TG and TG-FTIR. The addition of both MOFs decreased the enthalpy of fusion and enthalpy of curing by 60%. The addition of copper MOF to SPE drastically reduced the temperature at which the thermal curing was maximum (300 °C to 252 °C). The 2-H chromenes were formed from bispropargyl ethers by Claisen-type sigmatropic rearrangement. Compared to pure SPE, the polymers resulting from hybrid systems show a slower thermal degradation rate. The sulfone as a swivel group in SPE and the involvement of fumarate π-bonds of MOFs during polymerization make the material more versatile. The investigation concluded that these novel inorganic–organic hybrid blends may be a good start for low-temperature curable sufficiently thermally stable matrix resin systems having a wide scope of applicability in the field of filler-reinforced composites. [ABSTRACT FROM AUTHOR]

Keywords: chiral allene; medium-sized ring; cycloaddition; Cope rearrangement; asymmetric catalysis EN chiral allene medium-sized ring cycloaddition Cope rearrangement asymmetric catalysis 1845 1851 7 09/15/23 20231004 NES 231004 Graph 1 Introduction Allene is a unique functional group with a three-carbon structure consisting of two I sp i SP 2 sp -hybridized terminal carbons and one I sp i -hybridized inner carbon (Scheme 1a). Since the correct structure and axial chirality of allenes was first predicted by the pioneer van't Hoff in 1875, [2] allenes have attracted continuous research interest from synthetic chemists for over a century, driven by the curiosity of their unique structure. [24] Another method to synthesize the 1,3-endocyclic allenes is the cyclization of skillfully designed acyclic allenes; but this is not applicable to the preparation of cyclic allenes with smaller rings. [Extracted from the article]

Experimental data on the use of a wide range of polyaniline (PANI) derivatives as a sensitive material in humidity sensors are presented. The influence of various structural factors, such as the nature and structure of substituents, on the sensitivity to environmental humidity has been investigated. The use of PANI derivatives as a sensitive material in resistive sensors demonstrated a high response of electrical conductivity to humidity changes. It has been established that the modification of PANI by introduction of a substituent into the aromatic ring not only improves the solubility, but also increases the sensitivity of the material to environmental humidity due to the formation of a structure with a large surface area. [ABSTRACT FROM AUTHOR]

The synthesis of functional and complex organic compounds is majorly performed by the Claisen rearrangement method. Claisen rearrangement is one of [3,3] sigmatropic rearrangements, a complex method in the synthesis of organic compounds, where it is mostly used to construct stereoselective compounds. It can be combined with other synthesis methods to synthesize organic compounds giving satisfactory results based on the method used, temperature, time, and yield produced. This review aimed to summarize several recent advances in synthesizing organic compounds through Claisen rearrangement reactions. An understanding of the mechanism and applications of this reaction might improve the ability to synthesize innovative and useful organic compounds in various fields of life sciences.

Owing to its unique physical properties, fluorine is often used to open up new reaction channels. In this report, we establish a cooperation of [5,5]‐rearrangement and fluorine‐assisted temporary dearomatization for arene multi‐functionalization. Specifically, the [5,5]‐rearrangement of fluoroaryl sulfoxides with β,γ‐unsaturated nitriles generates an intriguing dearomatized sulfonium species which is short‐lived but exhibits unusually high electrophilicity and thus can be instantly trapped by nucleophiles and dienes at a remarkably low temperature (−95 °C) to produce four types of valuable multi‐functionalized benzenes, respectively, involving appealing processes of defluorination, desulfurization, and sulfur shift. Mechanistic studies indicate that the use of fluorine on arenes not only circumvents the generally inevitable [3,3]‐rearrangement but also impedes the undesired rearomatization process, thus provides a precious space for constructing and elaborating the temporarily dearomatized fluorinated sulfonium species. [ABSTRACT FROM AUTHOR]

We present a step-economical divergent synthetic approach for isoflavene derivatives using the Suzuki–Miyaura cross coupling of a 3-boryl-2H-chromene and three aryl bromides. 3-Boryl-2H-chromene, which is not a well-explored species, was prepared via Miyaura–Ishiyama borylation of a 3-chloro-2H-chromene obtained through a Claisen rearrangement cyclization cascade reaction. Further conversion of the cross-coupling products, three isoflavene derivatives, afforded three isoflavonoid natural products with one or two additional reaction steps.The use of 3-boryl-2H-chromene as the key intermediate for divergent Suzuki–Miyaura cross coupling reactions with aryl bromides enabled a step-economical approach to isoflavenes. [ABSTRACT FROM AUTHOR]

1,n‐dicarbonyls are one of the most fascinating chemical feedstocks finding abundant usage in the field of pharmaceuticals. Besides, they are utilized in a plethora of synthesis in general synthetic organic chemistry. A number of 'conventional' methods are available for their synthesis, such as the Stetter reaction, Baker‐Venkatraman rearrangement, oxidation of vicinal diols, and oxidation of deoxybenzoins, synonymous with unfriendly reagents and conditions. In the last 15 years or so, photocatalysis has taken the world of synthetic organic chemistry by a remarkable renaissance. It is fair to say now that everybody loves the light and photoredox chemistry has opened a new gateway to organic chemists towards milder, more simpler alternatives to the previously available methods, allowing access to many sensitive reactions and products. In this review, we present the readers with the photochemical synthesis of a variety of 1,n‐dicarbonyls. Diverse photocatalytic pathways to these fascinating molecules have been discussed, placing special emphasis on the mechanisms, giving the reader an opportunity to find all these significant developments in one place. [ABSTRACT FROM AUTHOR]

A concise and highly diastereoselective bioinspired key cationic cyclization strategy for the asymmetric synthesis of the tricyclic core of the (−)‐stemoamide, together with 8,9‐bis‐epi‐stemoamide has been described. The key N‐acyliminium ion precursors were accessed from L‐tartaric acid and L‐malic acid respectively. The use of ethyl acetoacetate derived bifunctional allylidenetriphenylphosphorane reagent in the early stage of the synthetic strategy is advantageous for the rapid construction of highly functionalized key pyrrolo[1,2‐α]azepine frameworks. [ABSTRACT FROM AUTHOR]

We report a cobalt‐catalyzed Wagner–Meerwein rearrangement of gem‐disubstituted allylarenes that generates fluoroalkane products with isolated yields up to 84 %. Modification of the counteranion of the N‐fluoropyridinium oxidant suggests the substrates undergo nucleophilic fluorination during the reaction. Subjecting the substrates to other known metal‐mediated hydrofluorination procedures did not lead to observable 1,2‐aryl migration. Thus, indicating the unique ability of these cobalt‐catalyzed conditions to generate a sufficiently reactive electrophilic intermediate capable of promoting this Wagner–Meerwein rearrangement. [ABSTRACT FROM AUTHOR]

The possibility for AuIII σ‐cyclopropyl complexes to undergo ring‐opening and give π‐allyl complexes was interrogated. The transformation was first evidenced within (P,C)‐cyclometalated complexes, it occurs within hours at −50 °C. It was then generalized to other ancillary ligands. With (N,C)‐cyclometalated complexes, the rearrangement occurs at room temperature while it proceeds already at −80 °C with a dicationic (P,N)‐chelated complex. Density Functional Theory (DFT) calculations shed light on the mechanism of the transformation, a disrotatory electrocyclic ring‐opening. Intrinsic Bond Orbital (IBO) analysis along the reaction profile shows the cleavage of the distal σ(CC) bond to give a π‐bonded allyl moiety. Careful inspection of the structure and bonding of cationic σ‐cyclopropyl complexes support the possible existence of C−C agostic interactions at AuIII. [ABSTRACT FROM AUTHOR]

The possibility for AuIII σ‐cyclopropyl complexes to undergo ring‐opening and give π‐allyl complexes was interrogated. The transformation was first evidenced within (P,C)‐cyclometalated complexes, it occurs within hours at −50 °C. It was then generalized to other ancillary ligands. With (N,C)‐cyclometalated complexes, the rearrangement occurs at room temperature while it proceeds already at −80 °C with a dicationic (P,N)‐chelated complex. Density Functional Theory (DFT) calculations shed light on the mechanism of the transformation, a disrotatory electrocyclic ring‐opening. Intrinsic Bond Orbital (IBO) analysis along the reaction profile shows the cleavage of the distal σ(CC) bond to give a π‐bonded allyl moiety. Careful inspection of the structure and bonding of cationic σ‐cyclopropyl complexes support the possible existence of C−C agostic interactions at AuIII. [ABSTRACT FROM AUTHOR]

The possibility for AuIII σ‐cyclopropyl complexes to undergo ring‐opening and give π‐allyl complexes was interrogated. The transformation was first evidenced within (P,C)‐cyclometalated complexes, it occurs within hours at −50 °C. It was then generalized to other ancillary ligands. With (N,C)‐cyclometalated complexes, the rearrangement occurs at room temperature while it proceeds already at −80 °C with a dicationic (P,N)‐chelated complex. Density Functional Theory (DFT) calculations shed light on the mechanism of the transformation, a disrotatory electrocyclic ring‐opening. Intrinsic Bond Orbital (IBO) analysis along the reaction profile shows the cleavage of the distal σ(CC) bond to give a π‐bonded allyl moiety. Careful inspection of the structure and bonding of cationic σ‐cyclopropyl complexes support the possible existence of C−C agostic interactions at AuIII. [ABSTRACT FROM AUTHOR]

The possibility for AuIII σ‐cyclopropyl complexes to undergo ring‐opening and give π‐allyl complexes was interrogated. The transformation was first evidenced within (P,C)‐cyclometalated complexes, it occurs within hours at −50 °C. It was then generalized to other ancillary ligands. With (N,C)‐cyclometalated complexes, the rearrangement occurs at room temperature while it proceeds already at −80 °C with a dicationic (P,N)‐chelated complex. Density Functional Theory (DFT) calculations shed light on the mechanism of the transformation, a disrotatory electrocyclic ring‐opening. Intrinsic Bond Orbital (IBO) analysis along the reaction profile shows the cleavage of the distal σ(CC) bond to give a π‐bonded allyl moiety. Careful inspection of the structure and bonding of cationic σ‐cyclopropyl complexes support the possible existence of C−C agostic interactions at AuIII. [ABSTRACT FROM AUTHOR]

Carbon‐carbon bond formation in the phenanthridine 7‐position was achieved by microwave‐assisted Claisen rearrangement of 8‐allyloxyphenanthridines. The reactions took place with excellent regioselectivity and high chemical yields. If the 7‐position was substituted, rearrangement to C‐9 took place, but the reaction occurred less readily. Rearrangements of 8‐allyloxy‐5,6‐dihydrophenanthridines (phenanthridines with a saturated B‐ring) gave a mixture of 7‐ and 9‐substituted products. The experimental results were supported by DFT (density functional theory) calculations. [ABSTRACT FROM AUTHOR]

Abstract Carbon‐carbon bond formation in the phenanthridine 7‐position was achieved by microwave‐assisted Claisen rearrangement of 8‐allyloxyphenanthridines. The reactions took place with excellent regioselectivity and high chemical yields. If the 7‐position was substituted, rearrangement to C‐9 took place, but the reaction occurred less readily. Rearrangements of 8‐allyloxy‐5,6‐dihydrophenanthridines (phenanthridines with a saturated B‐ring) gave a mixture of 7‐ and 9‐substituted products. The experimental results were supported by DFT (density functional theory) calculations.

Merging the latest advances in the field of gold catalysis and the efficiency of hexafluoro‐2‐propanol (HFIP), a gold‐catalyzed orthogonal tandem reaction has been developed to access carbocyclic ketone on naphthalene substrates. The methodology involved a cycloisomerization/nucleophilic addition and a C→O rearrangement. The HFIP solvent most probably acted as a Lewis‐acid on isochromene derivatives, through hydrogen donor bond activity. A large range of acenaphthylene carbaldehyde has been engaged in this process coupling gold catalysis and Lewis‐acid behavior of HFIP leading to cyclic ketones with a yield ranging from 15 to 91% (27 compounds). The mechanism was investigated, and the reaction most presumably occurred via a classical cyclization process followed by a [Au]‐HFIP interaction for the final rearrangement. The interest of such transformation was demonstrated by performing it on a gram‐scale. Moreover, a post‐functionalization bromination was performed, as well as the isomerization of some functionalized ketones leading to full trans derivatives with a yield ranging from 78 to 90% yields. [ABSTRACT FROM AUTHOR]

The total synthesis of lucidumone (1), a Ganoderma meroterpenoid, was accomplished in racemic form from easily prepared 6 and 7 in 10 steps as the longest linear sequence. The synthesis was completed through one‐pot preparation of the tetracyclic core skeleton by Claisen rearrangement followed by an intramolecular aldol reaction. The intramolecular aldol reaction allowed for the stereocontrolled construction of the bicyclo [2.2.2] octane skeleton fused to an indanone structure. The enantioselective total synthesis of 1 was also described via a chiral transfer strategy in the Claisen rearrangement. [ABSTRACT FROM AUTHOR]

A novel and convenient approach for the synthesis of vinyl phosphonates has been developed, utilizing an aromatic aza-Claisen rearrangement of β,γ-unsaturated α-aminophosphonates. The synthetic utility of this method was further examined in a gram-scale synthesis. The DFT calculations have provided insights into the basis of the reaction mechanism. [ABSTRACT FROM AUTHOR]

Herein, we have developed a sequential visible-light-promoted Wolff rearrangement of 1-diazonaphthalen-2(1H)-ones, followed by capturing the in situ generated ketene intermediates with various alcohols, producing diverse 1H-indene-3-carboxylates in moderate to good yields under mild reaction conditions. The broad substrate scope, high functional group tolerance, and robust conditions make the resulting derivative a versatile platform for the synthesis of plenty of bioactive molecules. [ABSTRACT FROM AUTHOR]

The asymmetric total synthesis of two sesquiterpenoids, (−)‐HM‐3 and (−)‐HM‐4, isolated from a phytopathogenic fungus, has been developed using a gold‐catalyzed [3,3]‐sigmatropic rearrangement of sulfonium as key step. During this transformation, an excellent chirality transfer was observed between the chiral sulfoxide substrate and the newly formed quaternary stereogenic center with 96 % enantiomeric excess. The implementation of this efficient methodology allowed us to isolate the two natural products in only 7–8 chemical steps with overall yields reaching 12–16 %. [ABSTRACT FROM AUTHOR]

We propose a simple procedure for visualising the electron density changes (EDC) during a chemical reaction, which is based on a mapping of rectangular grid points for a stationary structure into (distorted) positions around atoms of another stationary structure. Specifically, during a small step along the minimum energy pathway (MEP), the displacement of each grid point is obtained as a linear combination of the motion of all atoms, with the contribution from each atom scaled by the corresponding Hirshfeld weight. For several reactions (identity S N 2, Claisen rearrangement, Diels-Alder reaction, [ 3 + 2 ] cycloaddition, and phenylethyl mercaptan attack on pericosine A), our EDC plots showed an expected reduction of electron densities around severed bonds (or those with the bond-order lowered), with the opposite observed for newly-formed or enhanced chemical bonds. The EDC plots were also shown for copper triflate catalyzed N 2 O fragmentation, where the N–O bond weakening initially occurred on a singlet surface, but continued on a triplet surface after reaching the minimum-energy crossing point (MECP) between the two potential energy surfaces. [ABSTRACT FROM AUTHOR]