Search

An organocatalyzed Fischer indolization is established by combining 2,2′-biphenol (10 mol%) and B(OH)3 (30 mol%) as weak, readily available, and easy-to-handle acids. The inclusion of MgSO4 , which efficiently scavenges NH3 (a possible acid catalyst poison), appears to be key to the success of this process. The corresponding indoles are obtained in yields of up to 91% using this method.y [ABSTRACT FROM AUTHOR]

A facile one-pot multicomponent reaction employing aromatic aldehydes, malononitrile, and phthalhydrazide in H2O and EtOH (1:1) mixture at 80ºC has been innovated for the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones. This approach stands out for its simplicity, ease of execution, and high efficiency. The reaction employs 20 mol% of imidazole as an organocatalyst, enhancing its practicality and applicability. A total of 14 compounds were synthesized within 0.5 to 4 h under a greener reaction medium, with the yields of products ranging from 85–94%. The key components of this protocol are the use of H2O:EtOH (1:1) mixture as green solvent, recyclable reaction medium, imidazole as an organocatalyst, mild reaction conditions, easy isolation of products, good to excellent yields, and no column chromatographic purification. Using the microbial dilution method, all the synthesized compounds underwent evaluation for their antibacterial activity against a spectrum of strains, including E. coli, S. aureus, P. aeruginosa, B. subtilis, as well as antifungal activity against A. flavus and A. niger. The synthesized derivatives exhibited diverse inhibitory effects on the growth of both bacterial and fungal strains, showcasing their potential utility across various microbial targets. A simple one-pot multicomponent reaction using substituted aromatic aldehydes, malononitrile, and phthalhydrazide in 10 ml of H2O and EtOH (1:1) mixture at 80ºC for the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives has been developed. This methodology involves the use of greener solvents and imidazole as an organocatalyst which leads to good to excellent yields of the products with less reaction time. [ABSTRACT FROM AUTHOR]

We rationally designed and successfully developed novel dipeptidic proline amide–isothiouronium catalysts for asymmetric conjugate addition reactions between various aldehydes and nitroolefins, which generated 1,4‐addition products with up to 95% yields, 92:8 syn‐diastereoselectivity, and 96% enantiomeric excess. The catalysts, which were prepared via simple methylation of the corresponding thiourea, can provide the desired enantiomeric syn‐1,4‐adducts by exchanging the configuration of the N‐terminal proline moiety. [ABSTRACT FROM AUTHOR]

Both enantiomers of functionalized Hajos–Parrish ketone (HPK) analogs were prepared with excellent diastereoselectivities and enantioselectivities using the same chiral catalyst under two slightly different conditions. In condition A, dioxane was used as the solvent with 3 equivalents of water. In condition B, acetonitrile was used as the solvent with 30 equivalents of water, followed by epimerization with a base in a one‐pot. The reaction consisted of a domino reaction including a diphenylprolinol silyl ether–mediated asymmetric Michael reaction and an intramolecular Henry reaction. In the Michael reaction, depending on the solvent and water amounts, syn‐ and anti‐isomers were selectively synthesized with excellent enantioselectivity, in which the absolute configuration at C5 (indanone numbering) was opposite. The subsequent Henry reaction was diastereoselective, in which the C5 substituent controlled the three chiral centers in a highly diastereoselective manner. The final base treatment in condition B caused epimerization, changing the configuration at C6. Switching more than two chiral centers with high enantioselectivity is extremely difficult using the same chiral catalyst; the present reaction is a very rare enantiodivergent reaction that switches five continuous chiral centers with high enantioselectivity. [ABSTRACT FROM AUTHOR]

A diaminomethylenemalononitrile organocatalyst efficiently promoted the asymmetric conjugate addition of cyclic β‐keto esters to (E)‐β‐nitroacrylate derivatives, yielding the corresponding β‐nitro esters derivatives with excellent enantioselectivities (up to >99 % ee). This is the first successful example of highly stereoselective conjugate addition of cyclic β‐keto esters to (E)‐β‐nitroacrylate derivatives to obtain anti‐isomers. [ABSTRACT FROM AUTHOR]

Chiral N‐heterocyclic compounds are key structures in natural compounds and pharmaceuticals, and they serve as essential building blocks of functional materials. Catalytic asymmetric cycloaddition reactions represent one of the most efficient synthetic strategies for constructing optically active heterocycles. Cyclic sulfamidate imines have recently come to be extensively studied and widely utilized in both organocatalytic and transition metal‐catalyzed asymmetric cycloadditions, where they have been shown to provide various N‐fused‐heterocycles and spiro‐cycles exhibiting high efficiencies with excellent stereoselectivities. This review highlights recent advancements in catalytic asymmetric cycloadditions of cyclic sulfamidate imines for the stereoselective synthesis of biologically active sulfamidate‐containing heterocycles since 2012 while focusing on the diverse reactivities of cyclic sulfamidate imines and the mechanisms of chiral induction in catalysis. [ABSTRACT FROM AUTHOR]

Chiral monosubstituted cyclohexanediamine catalyst, namely (1R,2R)-2-(piperidin-1-yl)cyclo-hexan-1-amine (Cat1) has been efficiently synthesized and used to catalyze the aldol reaction of cyclohexanone and 2-(trifluoromethyl)benzaldehyde to obtain (R)-2-{(S)-hydroxy[2-(trifluoromethyl)phenyl]methyl}cyclo-hexan-1-one. The catalyst (20 mol %) provided high yield (up to 85%) and excellent enantioselectivity (95.6% ee) in water solution in three parallel tests. [ABSTRACT FROM AUTHOR]

Objectives: Salophen-type Schiff bases functionalized with 4-(dimethylamino)pyridinium halide units are shown to be effective single-component catalysts for the synthesis of cyclic carbonates from terminal epoxides and carbon dioxide. Methods: Using one of such trifunctional organocatalysts, epichlorohydrin could be selectively converted to the target cyclic carbonate under 2 bar of CO2 at 120 °C. Results: Over 80% conversion of E3 was then observed when organocatalyst S3 was used in the amount of 0.5 mol% (TON = 156) and even the use of 0.05 mol% S3 guaranteed almost 50% conversion of E3 to C3 (TON = 893). Conclusions: The presence of tertiary amine units in the molecules of these homogeneous organocatalysts proved to be crucial for the catalytic activity of developed organocatalysts. However, their catalytic activity was also supported by the presence of acidic phenolic units and halide ions as Lewis bases. Some closely related compounds were found to be clearly less active or inactive catalytically under the applied reaction conditions. [ABSTRACT FROM AUTHOR]

A chiral sodium glycerophosphate is successfully exploited as a catalyst in the Michael addition of methyl malonate to a number of chalcones. The reactions supplied the target adducts in satisfactory yields and good enantiomeric excesses. A tentative computational study is presented, aiming to understand the reaction mechanism. [ABSTRACT FROM AUTHOR]

Novel ultrathin Cd-Ag-MOF@ZnO composite nanoribbons (Ut-Nr Cd-Ag-MOF@ZnO C) were prepared and characterized in this research to serve as organocatalyst in Hantzsch condensation for selective synthesis of asymmetric polyhydroquinolines through a one-pot multi-component condensation reaction of various substituted arylaldehyde, 5,5-dimethyl-1,3-cyclohexanedione, ammonium acetate and ethyl acetoacetate under solvent-free conventional heating in relatively short reaction times. The developed catalysts were easily recycled and reutilized at least three times under optimized reaction conditions with no noticeable decline in their initial catalytic activities. Operational simplicity and environmental compatibility, combined with the application of a reusable and affordable heterogeneous catalyst, significant efficiency, relatively short reaction time, and good yield are among the main characteristics of the proposed synthetic approach. [ABSTRACT FROM AUTHOR]

Conformational freedom-restricted peptides, such as stapled peptides, play a crucial role in the advancement of functional peptide development. We synthesized stapled octapeptides using α-carbocyclic α,α-disubstituted α-amino acids, particularly 3-allyloxy-1-aminocyclopentane-1-carboxylic acid, as the crosslink motifs. The organocatalytic capabilities of the synthesized stapled peptides were assessed in an asymmetric nucleophilic epoxidation reaction because the catalytic activities are known to be proportional to α-helicity. Despite incorporating side-chain crosslinks, the enantioselectivities of the epoxidation reaction catalyzed by stapled octapeptides were found to be comparable to those obtained using unstapled peptides. Interestingly, the stapled peptides using α-carbocyclic α,α-disubstituted α-amino acids demonstrated higher reactivities and stereoselectivities (up to 99% ee) compared to stapled peptides derived from (S)-α-(4-pentenyl)alanine, a commonly used motif for stapled peptides. These differences could be attributed to the increased α-helicity of the former stapled peptide in contrast to the latter, as evidenced by the X-ray crystallographic structures of their N-tert-butoxycarbonyl derivatives. [ABSTRACT FROM AUTHOR]

Chromene derivatives are important oxygen heterocycles, which are met in numerous natural products, pharmaceuticals, and organic functional materials. This review survey the achievements in the synthesis of chromene derivatives from α,β‐unsaturated aldehydes. Particular attention is paid to the use of catalytic systems, synthetic advantages and mechanistic aspects of the reactions. The works published over the past 15 years are covered. [ABSTRACT FROM AUTHOR]

3‐methyl‐4‐(hetero)arylmethylidene isoxazole‐5(4H)‐one derivatives (4a‐r) derivatives (4a‐r) were synthesized by the multi‐component reactions. The multi‐component reactions (MCRs) of hydroxylamine hydrochloride, ethyl acetoacetate and aromatic/ heteroaromatic aldehyde catalyzed by novel Glutamic acid (Glu) as a biodegradable and eco‐friendly organocatalyst in ethanol on oil bath stirring at 60 °C. The final product homogeneity was examined by various spectroscopic techniques. In this work prepared compounds 4 q and 4 r are novel derivatives. The molecular dynamics of total energy and energy gap was calculated using DFT/B3LYP/6–31G (dp) method. The selected derivatives (4 l–r) screened against in vitro MCF‐7 breast cancer cell line by MTT assay, derivatives 4 l and 4 o displayed very good activity with IC50 of 6.57±2.31, and 21.93±1.34 as compared to doxorubicin of IC50 (3.69±0.17). Molecular docking studies were performed to evaluate interaction of PDB id: 1 M17 with led molecules of MCF‐7. Later, 1 M17 and 4 l underwent 200 ns molecular dynamics and simulation within physiological conditions, the outcomes showed that during the simulation, the ligand stayed in the same form. Further, the selected derivatives drug like computed using swissADME, and derivatives 4 l–r obeyed rule of Lipinski's. Furthermore, selected derivatives tested for electrochemical behavior using cyclic voltammetry, and compound 4 l and 4 q showed strong oxidation and reduction potential, thus these derivatives can present better antioxidant properties. [ABSTRACT FROM AUTHOR]

Click chemistry has emerged as a versatile and robust polymerization technique for the construction of functional polymers. In this work, organocatalyst-mediated consecutive thiol-yne and thiol-ene click reactions were performed for the synthesis and modification of the electron-deficient poly(vinylene sulfide) (PVS) structure. PVS was prepared within an hour in the presence of 1,4-diazabicyclo[2.2.2] octane (DABCO) and in an anti-Markovnikov fashion, with a high molecular weight (Mn = 12.9 kDa) and high stereoregularity (88% E-isomer). Following various optimization studies using 1-propanethiol as the model thiol, the obtained PVS was modified with various thiols in chloroform for 10 min using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the catalyst, resulting in thioacetal main chain polymers. The scope of thiols used in the modification studies spans from alkyl and cycloalkyl to aromatic and allylic, and the polymers were obtained with varying efficiencies. Primary alkyl and aromatic thiols exhibited high efficiencies ranging from 87% to 100%. Similar high efficiencies were found for secondary mercaptans (70% and 92%); however, a very low efficiency (5%) was found for a tertiary mercaptan due to steric hindrance. It is believed the proposed indirect polythioacetal synthesis method holds the potential to be utilized in bio-related applications and material science. [ABSTRACT FROM AUTHOR]

It is highly desirable to develop simple organocatalysts for the controlled ring-opening alternating copolymerization (ROAC) of epoxides and cyclic anhydrides, leading to high molecular weight polyesters. Hence, a phosphazenium salt, namely tri[tris (dimethylamino)phosphoranylidenamino]phosphonium chloride (P4+Cl−), is developed as a catalyst for the ROAC of epoxides and cyclic anhydrides. Surprisingly, the combination of P4+Cl− with a protonic initiator, such as 1,4-benzenedimethanol (BDM) exhibited high efficiency in the copolymerization of propylene oxide (PO) and phthalic anhydride (PA). This led to the production of polyester with an exceptional high molecular weight (Mn) of up to 126 kDa, which represented a rare example of poly(PO-alt-PA) with Mn surpassing 100 kDa. Note that the core P atom is trivalent status and the tris[tris(dimethylamino)] phosphoranyl group will share one proton in the P4+Cl− salt. Once combined with protonic species, the P4+Cl− will not only serve as a proton acceptor but also as a hydrogen bonding donor for the cyclic anhydrides. Therefore, it was assumed that the P4+ plus proton served dual role in mimic of base/urea pair to effectively catalyze ROAC, which was supported by density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

An efficient organocatalytic cascade vinylogous Michael‐cyclization to construct the challenging full substituted cyclohexa‐1,3‐dienes has been developed. Catalyzed by the cinchona alkaloids‐derived thiourea VIII at −60 °C, the products were obtained as a single diastereomer with two contiguous stereocenters and more than four different useful functional groups in moderate to good yields and good to excellent enantioselectivities. [ABSTRACT FROM AUTHOR]

Herein, we report thiouracil‐catalyzed α‐selective O‐glycosylations employing easily accessible glycosyl trichloroacetimidate donors without using any co‐catalyst or additive. A variety of alcohol nucleophiles including saccharides, and amino acids with different protecting groups containing glycosyl trichloroacetimidate donors were successfully α‐glycosylated using an operationally simple protocol. Moreover, mechanistic investigations suggest that thiouracil functions as Brønsted acid/base catalyst in this glycosylation process. [ABSTRACT FROM AUTHOR]

Organic photocatalysts frequently possess dual singlet and triplet photoreactivity and a thorough photochemical characterization is essential for efficient light-driven applications. In this article, the mode of action of a polyazahelicene catalyst (Aza-H) was investigated using laser flash photolysis (LFP). The study revealed that the chromophore can function as a singlet-state photoredox catalyst in the sulfonylation/arylation of styrenes and as a triplet sensitizer in energy transfer catalysis. The singlet lifetime is sufficiently long to exploit the exceptional excited state reduction potential for the activation of 4-cyanopyridine. Photoinduced electron transfer generating the radical cation was directly observed confirming the previously proposed mechanism of a three-component reaction. Several steps of the photoredox cycle were investigated separately, providing deep insights into the complex mechanism. The triplet-excited Aza-H, which was studied with quantitative LFP, is formed with a quantum yield of 0.34. The pronounced triplet formation was exploited for the isomerization reaction of (E)-stilbene to the Z-isomer and the cyclization of cinnamyl chloride. Catalyst degradation mainly occurs through the long-lived Aza-H triplet (28 µs), but the photostability is greatly increased when the triplet efficiently reacts in a catalytic cycle such that turnover numbers exceeding 4400 are achievable with this organocatalyst.

Intramolecular benzoin condensation, which is a powerful and useful method for the formation of carbon−carbon bonds from aldehydes, is also an advantageous method for the preparation of a wide variety of α‐hydroxy ketones. The α‐Hydroxy carbonyl groups are an important structure for natural products, industrial, and pharmaceutical materials. In this study, it was aimed to synthesize new bulky α‐hydroxy ketones that can be used both as pharmaceutical materials and can lead to the synthesis of new organocatalysts. An effective method was applied for the synthesis of bulky hydroxy ketones 2 a–l using intramolecular benzoin condensation catalyzed by N‐heterocyclic carbene (I) from 4‐arenoxybenzaldehyde 1 a–f or 4‐thioetherbenzaldehyde 1 g–l derivatives and 12 new bulky α‐hydroxy ketone compounds 2 a–l were synthesized in 70–87 % isolated yield. The synthesized compounds were characterized by spectroscopic and chromatographic methods such as FT‐IR, NMR, LC–MS, and CHN analysis. Additionally, compound 2 h selected as a model substrate was converted into 1,2 diol 3 h, 1,2‐diketone 4 h, and 1,2‐keto acetate 5 h derivatives, and structural analyses were performed. Moreover, chiral hydroxy ketone 2 h was obtained with 100 % ee due to the enzymatic hydrolysis reaction catalyzed by Lipase from Candida rugosa (CRL). [ABSTRACT FROM AUTHOR]

Potassium phthalimide (PPI) and Potassium phthalimide-N-oxyl (POPINO) have emerged as a versatile and efficient catalyst in various organic synthesis reactions, playing a crucial role in the development of sustainable and environmentally friendly synthetic methodologies. This review highlights the catalytic applications of PPI and POPINO in diverse transformations, showcasing its potential as a valuable tool in modern organic synthesis. The multifaceted reactivity of PPI and POPINO has been explored in reactions such as nucleophilic substitutions, condensations, cycloadditions, and oxidation processes, making it an attractive catalyst for the synthesis of complex organic molecules. [ABSTRACT FROM AUTHOR]

The first chemoselective C4‐benzylation of 5‐aminopyrazoles, utilizing a 3 mol% squaric acid catalyst, is disclosed. In this process, ortho‐quinone methides are efficiently generated from 2‐hydroxybenzyl alcohols in water under mild conditions. This method successfully delivers a wide range of C4‐benzylated 5‐aminopyrazoles, achieving moderate to excellent yields while demonstrating high chemoselectivity, which is further confirmed by mechanistic studies. Notably, the protocol uses water as an eco‐friendly solvent, requires a low organocatalyst loading, and eliminates the need for column chromatography. [ABSTRACT FROM AUTHOR]

Dihydroquinolin‐2‐ones, recognized for their bioactive properties, feature a six‐membered structure with nitrogen‐containing heterocycles. A method has been developed for synthesizing enantioenriched 3,4‐dihydroquinoline‐2‐one derivatives. This approach utilizes an asymmetric [4+2]‐cyclization process, combining 2‐amino‐β‐nitrostyrenes with azlactones, and is facilitated by a bifunctional squaramide‐based organocatalyst. This process has enabled the creation of chiral 3,4‐dihydroquinoline‐2‐ones with complex structures, including chiral tetrasubstituted carbon stereocenters, delivering corresponding products in 26–95% yield with a diastereomeric ratio of 1.2:1–19:1 and 52–97 ee. [ABSTRACT FROM AUTHOR]

This article discusses the diastereoselective synthesis of carbohydrate conjugates with pyrano[3,2-c]quinolone motifs, which are known for their pharmacological properties. The researchers aim to optimize the synthesis process by exploring different reaction conditions and catalysts. They successfully synthesized pyrano[3,2-c]quinolones with high diastereoselectivity using Perlin aldehyde and l-proline as an organocatalyst. The structures of the compounds were confirmed through spectral data analysis and the stereochemistry was verified through experiments. The synthesis process was scalable and yielded sixteen novel carbohydrate conjugates. The article also provides detailed information on the synthesis and characterization of specific compounds, including their physical properties and spectroscopic data. The compounds are potential candidates for further biological evaluation. [Extracted from the article]

We develop a new l-proline-Brønsted acid deep eutectic mixture (DEM)-driven straightforward protocol for the synthesis of (aryl/heteroarylmethylene)bis(3-hydroxy-5,5-dimethylcyclo-hexenone) derivatives with broad functional group compatibility using one-pot consecutive Claisen–Schmidt and Michael addition reactions. These derivatives are obtained under very mild reaction conditions with good yields (65–92%) in a short span (20–30 min). Significantly, a newly developed l-proline-Brønsted acid catalyst system was characterized using D2O exchange proton NMR spectroscopy. [ABSTRACT FROM AUTHOR]

This work describes an efficient, concise, and green sonochemical synthesis of benzylidene derivatives of enolizable carbonyls featuring barbituric acid derivatives, pyrazole-5-one, and rhodanine in aqueous ethanol using an organocatalyst. This method enables the synthesis of various benzylidene derivatives via a direct sp3 C–H olefination reaction of enolizable carbonyls. We remarkably emphasize the synthetic utility of these derivatives and validate the molecular structures using 1H-NMR and 13C-NMR spectroscopy (APT) as well as SC-XRD investigation of representative compounds. [ABSTRACT FROM AUTHOR]

The preparation of polythioethers has gained importance again after the development of click chemistry reactions. The thiol-X reactions, i.e., thiol-ene reactions based on free radical mechanism facilitated by light or heat, and thiol-Michael and thiol-epoxy reactions, which are the main synthetic pathways for the synthesis of polymers (linear, hyperbranched (HB), and network) with thioether linkages and meet most of the features of click reactions strategy, have currently been revisited. For a while, our group has focused on synthesizing linear, HB, and network polythioethers based on electron-deficient alkyne-containing precursors. We have shown that electron-deficient alkyne-containing monomers and polymers offer a suitable platform for thiol-Michael (i.e., thiol-yne) click reactions to yield linear, HB, and network structures rapidly under ambient conditions. The central structure in these polythioether syntheses is electron-deficient alkyne bonds of acetylenedicarboxylates, which are then reacted with dithiols in chloroform through an organobase 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) at ambient temperatures. Moreover, acetylenedicarboxylates are functionalized using copper-free azide-alkyne cycloaddition reaction followed by reacting with multifunctional allyl and SH derivatives through thiol-ene photopolymerization resulting in polymeric networks with thioether linkages. This feature article highlights our contribution to the synthesis of linear, HB, and network polythioether based on various electron-deficient alkyne precursors. [ABSTRACT FROM AUTHOR]

Biomimetic flavin catalysts enable green and selective aerobic oxidative transformations. However, most previous studies tended to focus on reproducing the enzymatic function of flavin monooxygenase, thereby limiting the applications of flavin catalysts to oxygen‐atom transfer reactions. We herein report a cross‐dehydrogenative coupling (CDC) between the sp3 C−H bond of tetrahydroisoquinolines and the sp3 and sp2 C−H bonds of carbon nucleophiles, such as α‐methylene carbonyl compounds, nitromethane, and indoles, for C−C bond formation promoted by flavin catalysts. Flavin catalysis enables the oxidative C−H activation of tetrahydroisoquinolines and the efficient activation of molecular oxygen (1 atm) under mild and metal/light‐free conditions, thus facilitating a green aerobic CDC that generates benign water as the sole by‐product. [ABSTRACT FROM AUTHOR]

We synthesized six new camphor-derived homochiral thioureas 1–6, from commercially available (1R)-(−)-camphorquinone. These new compounds 1–6 were evaluated as asymmetric organocatalysts in the stereoselective formation of glycosidic bonds, with 2,3,4,6-tetra-O-benzyl-D-glucopyranosyl and 2,3,4,6-tetra-O-benzyl-D-galactopyranosyl trichloroacetimidates as donors, and several alcohols as glycosyl acceptors, such as methanol, ethanol, 1-propanol, 1-butanol, 1-octanol, iso-propanol, tert-butanol, cyclohexanol, phenol, 1-naphtol, and 2-naphtol. Optimization of the asymmetric glycosylation reaction was achieved by modifying reaction conditions such as solvent, additive, loading of catalyst, temperature, and time of reaction. The best result was obtained with 2,3,4,6-tetra-O-benzyl-D-galactopyranosyl trichloroacetimidates, using 15 mol% of organocatalyst 1, in the presence of 2 equiv of MeOH in solvent-free conditions at room temperature for 1.5 h, affording the glycosidic compound in a 99% yield and 1:73 α:β stereoselectivity; under the same reaction conditions, without using a catalyst, the obtained stereoselectivity was 1:35 α:β. Computational calculations prior to the formation of the products were modeled, using density functional theory, M06-2X/6-31G(d,p) and M06-2X/6-311++G(2d,2p) methods. We observed that the preference for β glycoside formation, through a stereoselective inverted substitution, relies on steric effects and the formation of hydrogen bonds between thiourea 1 and methanol in the complex formed. [ABSTRACT FROM AUTHOR]

A diaminomethylenemalononitrile organocatalyst efficiently promoted the asymmetric conjugate addition of cyclic β‐keto esters to benzoyl acrylonitriles to afford the corresponding adducts. This was followed by the transformation of the nitrile group into an amide group, resulting in bicyclic γ‐lactam derivatives in good yields with excellent enantioselectivities (up to 99 % ee). As far as we know, this is the first study to synthesize chiral bicyclic γ‐lactam derivatives from cyclic β‐keto esters and benzoyl acrylonitriles. [ABSTRACT FROM AUTHOR]

A chiral sodium glycerophosphate is successfully exploited as a catalyst in the Michael addition of methyl malonate to a number of chalcones. The reactions supplied the target adducts in satisfactory yields and good enantiomeric excesses. A tentative computational study is presented, aiming to understand the reaction mechanism.

Conformational freedom-restricted peptides, such as stapled peptides, play a crucial role in the advancement of functional peptide development. We synthesized stapled octapeptides using α-carbocyclic α,α-disubstituted α-amino acids, particularly 3-allyloxy-1-aminocyclopentane-1-carboxylic acid, as the crosslink motifs. The organocatalytic capabilities of the synthesized stapled peptides were assessed in an asymmetric nucleophilic epoxidation reaction because the catalytic activities are known to be proportional to α-helicity. Despite incorporating side-chain crosslinks, the enantioselectivities of the epoxidation reaction catalyzed by stapled octapeptides were found to be comparable to those obtained using unstapled peptides. Interestingly, the stapled peptides using α-carbocyclic α,α-disubstituted α-amino acids demonstrated higher reactivities and stereoselectivities (up to 99% ee) compared to stapled peptides derived from (S)-α-(4-pentenyl)alanine, a commonly used motif for stapled peptides. These differences could be attributed to the increased α-helicity of the former stapled peptide in contrast to the latter, as evidenced by the X-ray crystallographic structures of their N-tert-butoxycarbonyl derivatives.

The preparation of a new class of six bifunctional thiourea organocatalysts having a D-fructose scaffold and a primary amino group was demonstrated. In the present study, the novel organocatalysts exhibited excellent enantio- and moderate diastereoselectivities in the asymmetric Michael addition of aliphatic ketones and 1,3-diketone to substituted nitroolefins at room temperature. In addition, the direct asymmetric aldol reaction between cyclic aliphatic ketone and aromatic aldehydes was also studied in the presence of the saccharide-thiourea organocatalysts giving excellent yield with moderate enantioselectivity.

As a crucial class of functional molecules in organosilicon chemistry, silanols are found valuable applications in the fields of modern science and will be a potentially powerful framework for biologically active compounds or functional materials. It has witnessed an increasing demand for non‐natural organosilanols, as well as the progress in the synthesis of these structural features. From the classic preparative methods to the catalytic selective oxidation of hydrosilanes, electrochemical hydrolysis of hydrosilanes, and then the construction of the most challenging silicon‐stereogenic silanols. This review summarized the progress in the catalyzed synthesis of silanols via hydroxylation of hydrosilanes in the last decade, with a particular emphasis on the latest elegant developments in the desymmetrization strategy for the enantioselective synthesis of silicon‐stereogenic silanols from dihydrosilanes. [ABSTRACT FROM AUTHOR]

A thiourea organocatalyst efficiently promoted the asymmetric cascade Michael/Michael reactions between isatin‐derived trifluoromethylacrylate and α‐alkylidene succinimide, resulting in high yields of spirooxindole derivatives. These compounds exhibit vicinal all‐carbon quaternary stereocenters and bear a trifluoromethyl group, with excellent enantioselectivities reaching up to 99 % ee. This work represents the first successful organocatalyst application for the direct construction of vicinal all‐carbon quaternary stereocenters, featuring a trifluoromethyl group. [ABSTRACT FROM AUTHOR]

The preparation of a new class of six bifunctional thiourea organocatalysts having a d-fructose scaffold and a primary amino group was demonstrated. In the present study, the novel organocatalysts exhibited excellent enantio- and moderate diastereoselectivities in the asymmetric Michael addition of aliphatic ketones and 1,3-diketone to substituted nitroolefins at room temperature. In addition, the direct asymmetric aldol reaction between cyclic aliphatic ketone and aromatic aldehydes was also studied in the presence of the saccharide-thiourea organocatalysts giving excellent yield with moderate enantioselectivity. [ABSTRACT FROM AUTHOR]

This article discusses the synthesis of C2'-sulfonylated quinine derivatives, which are novel organocatalysts. The authors successfully modified cinchona alkaloids at the quinoline moiety and synthesized various derivatives. These derivatives have the potential to be chiral organocatalysts and useful intermediates for further derivatization. The article provides detailed accounts of the synthetic routes used to produce specific compounds, along with their physical and spectroscopic properties. The information presented can be useful for researchers interested in the synthesis and potential uses of cinchona alkaloids. The authors of the article are Cheng-Yu Gu, Jie Zhou, Dong-Xing Tan, and Fu-She Han. [Extracted from the article]

(−)‐Quinine was synthesized in high enantio‐ and diastereoselectivity using an organocatalytic reaction as a key step. The piperidine skeleton was constructed using a diphenylprolinol silyl ether‐mediated Michael reaction, aza‐Henry reaction, and hemiacetalization in one‐pot. A reduction furnished the tri‐substituted piperidine with the correct stereochemistry in excellent diastereoselectivity. Introduction of a quinoline moiety and several transformations afforded (−)‐quinine. Using a stop‐and‐go method, (−)‐quinine was synthesized in 13 % yield with 12 pots. We further optimized the reactions for pot economy and achieved a synthesis of (−)‐quinine in 14 % yield using only five reaction vessels. Using 2,4‐dibromo‐6‐methoxyquinoline as a starting material enabled the preparation of C2′‐(−)‐quinine derivatives. [ABSTRACT FROM AUTHOR]

The present work is related to the synthesis of a carboxylic acid ester using lab synthesized triphenylphosphonium triflate catalyst and its application as a plasticizer for polyvinyl chloride (PVC) processing. The high thermal stability of this organocatalyst allows the synthesis of terephthalic acid di‐esters with high boiling alcohols such as 1‐butanol, 2‐ethyl hexanol with higher yield in the range of 55–97 %. Different ester derivatives like dioctyl phthalate (DOP), dioctyl terephthalate (DOTP), n‐butyl benzoate, dibutyl terephthalate, dibutyl phthalate, and di‐dodecanol terephthalate have been synthesized using triphenylphosphonium triflate organocatalyst. These synthesized ester derivatives are characterized using 1H NMR, GC‐MS and HPLC. The purity of different synthesized esters was in the range of 80–99 %. The synthesized Dioctyl terephthalate (DOTP) was used as a plasticizer in PVC and compared the results with commercial DOP plasticizer performance for PVC. The PVC/DOTP composition exhibited comparable performance in terms of mechanical properties like tensile and flexural strength and modulus. No significant change found in hardness and impact strength of both the compositions. Ease of processing observed in case of PVC/DOTP composition due to lower torque as compared to PVC/DOP composition. This indicates DOTP can be a potential alternative to the traditional dioctyl phthalate (DOP) plasticizer for PVC processing. [ABSTRACT FROM AUTHOR]

An efficient multi‐component synthesis of a wide range of pharmaceutically promising tetrasubstituted imidazoles has been reported using inexpensive and safe organocatalyst, ascorbic acid (Vitamin C). Imidazoles display a broad spectrum of activities in biological and pharmaceutical chemistry. Ascorbic acid, an highly effective H‐bond donor organocatalyst successfully accessed one‐pot imidazole synthesis via both three‐component and four‐component strategy. The core advantages of this approach include environmentally benign synthesis, good to excellent yield, high atom economy, use of easily available starting materials, operational simplicity. [ABSTRACT FROM AUTHOR]

Iodine and its hypervalent derivatives have emerged as versatile and environmentally friendly oxidative reagents in organic synthesis, offering efficient ways to form new bonds. However, the use of hypervalent iodine reagents is challenging, as they are unstable, potentially explosive, and costly. Therefore, hypoiodite species derived from onium iodites using safe and inexpensive oxidants are considered more promising for facilitating oxidative transformations. Nevertheless, applications of such catalytic systems are still limited in scope, especially for asymmetric reactions. In this concept paper, we described recent progress in chiral hypoiodite‐catalyzed enantioselective oxidative bond‐forming reactions, focusing on carbon–oxygen, carbon–nitrogen, and carbon–carbon bond formation reactions using ammonium and guanidinium salts as onium iodites. [ABSTRACT FROM AUTHOR]

L‐Prolinethioamide catalyzes direct stereoselective glycosylation of glycal donors to access 2‐deoxyglycosides under moderate reaction conditions. This proposed glycosylation protocol produced the desired products in up to 88% yield and shows greater tolerance of glycosyl acceptors and a broad substrate scope with better stereoselectivity. This method is also applicable for less nucleophilic acceptors such as phenol. In addition, 1,1′‐linked trehalose‐type analogues can also be accessed through this methodology. Further, mechanistic studies suggest that, in this glycosylation, L‐prolinethioamide operates via Brønsted acid/base catalysis. [ABSTRACT FROM AUTHOR]

An efficient sequential one‐pot, two‐step pseudo‐four‐component reaction between 3/4‐methyl N‐sulfonyl ketimines with 3‐chloropropiophenones triggered by DIPEA/NaHCO3 as a cooperative base and subsequent aza‐cyclization using NH4OAc is reported. This transition‐metal‐oxidant‐free technique concocts new C−C/C=C/C=N−C bonds selectively, guaranteeing acceptable yields of 2,3,6‐trisubstituted pyridines possessing ortho‐hydroxyaryl/benzenesulfonamide and propiophenone moieties at C2 and C3 positions, respectively. Interestingly, while replacing methyl‐substituents with straight alkyl chains of N‐sulfonyl ketimines, only a monoalkylation reaction happened with in situ‐generated vinyl ketones to deliver promising yields of 3‐picoline derivatives. Moreover, the synthetic transmutation of prepared pyridine derivative led to several important classes of pyridocoumarin, 5H‐chromenopyridine, and di(pyridin‐3‐yl) methane derivatives. [ABSTRACT FROM AUTHOR]

A facile, environmentally benign and proficient route has been developed for the diverse synthesis of pyrrolo[2,3-d]pyrimidine derivatives followed by heterocyclization starting from Amino uracil, arylgyoxal and malononitrile/thiols. Readily available thiamin hydrochloride organocatalyst was used as a green promoting medium. As well as the reaction progress was taken place under aqueous media. This procedure also offers a base and metal free approach which endowed high yields with better functional group tolerating ability and mild reaction conditions. Further, methodology had a widescope with recyclability and reuse of thiamin hydrochloride. DFT/TD-DFT calculations with B3LYP/6-311G++ level of theory were used to study the optimized geometry and HOMO-LUMO energy of the synthesized compounds (4b and 6i). [ABSTRACT FROM AUTHOR]

Herein, organocatalytically achieved polarity reversal of cationic bromine is presented. The proven bromocation source N‐bromosuccinimide (NBS) was converted to a superior bromoanion reagent by H/Br exchange with a secondary amine, substantiated with spectroscopic and computational evidence. The concept has further been used in a successfully accelerated organocatalyzed dibromination of olefins in a non‐hazardous, commercially viable process with a wide range of substrate scope. The reactivity of key entities observed through NMR kinetics and reaction acceleration using only 10 mol % of catalyst account for its major success. The nucleophilicity of the bromoanion was found to be superior in comparison to other nucleophiles such as MeOH and H2O also the protocol dominates over the competing allylic bromination reaction. [ABSTRACT FROM AUTHOR]

In this work, a rapid polymerization method was combined with thiol-para-fluoro (TPF) "click" post-polymerization modification (PPM) strategy. To this end, a reactive monomer, namely bis((perfluorophenyl)methyl) but-2-ynedioate, was specifically designed and used in the synthesis of polythioether via thiol-Michael addition reaction by using 1,6-hexanedithiol (HDT) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as a catalyst, and the reaction proceeded at room temperature for 5 min to give the pristine polythioether P0. This polymer was then used as a platform to perform PPM with various thiol compounds. The PPM reactions showed quantitative efficiency in 4 h with moderate to high yields. All modified polymers were analyzed with 1H, 13C, and 19F NMR analyses, and molecular weights were calculated by using GPC. It is believed that combining such polymerization and PPM reactions can be a very useful tool to obtain polymers having different structures for different purposes. Hence, this work introduces a new type of polymer backbone that can be rapidly prepared and undergo a relatively fast PPM. [ABSTRACT FROM AUTHOR]

Polylactide (PLA) is a fully bio‐derived polyester with great biodegradability, biocompatibility, and mechanical properties. Synthesis of stereoregular PLA by highly stereoselective organocatalyzed ring opening polymerization (ROP) of racemic lactide (rac‐LA) at room temperature is challenging despite some important developments in the past few years. In this contribution, two bulky phenyl diphosphazene bases, p‐PDPB and m‐PDPB, were conveniently synthesized by the Staudinger reaction. In combination with different hydrogen‐bond donors such as ureas and squaramides, they could mediate the stereocontrolled ROP of rac‐LA in THF at room temperature. Semicrystalline PLAs with narrow dispersity and high tacticity (Pm up to 0.84) were successfully synthesized in a well‐controlled manner using phenyl diphosphazene based/urea binary catalytic system. Structural analysis verified the linear structure and high end‐group fidelity of the resulting polymers. Moreover, the minimal transesterification of the polymer backbone proved by the MALDI‐TOF MS analysis indicated the good controllability of the phenyl diphosphazene based binary catalytic system. [ABSTRACT FROM AUTHOR]

This study deals with the synthesis of the regioselective and facile domino one-pot four-component reaction of 2-chloroquinoline-3-carbaldehydes, 1, 3-cyclodione compounds (as cyclic active methylene), ethyl acetoacetate (as β-keto ester), and hydrazine hydrate in the presence of DABCO as a homogeneous organocatalyst yielding a novel series of 4H-pyrano[2, 3-b]quinolones. This multicomponent reaction has some advantages; the significant one is C–O bond formation under metal-free conditions. Other benefits include simple procedure, mild and green condition, high yield, easy purification, and excellent regioselectivity. All polycyclic products (7a–k, 11 new compounds) were characterized by IR, 1H NMR, 13C NMR, and mass spectra. [ABSTRACT FROM AUTHOR]