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The photochemical reactivity of 1-bromo-2-oxo-1,2-dihydronaphthalene-1-carboxylates (BODNs) was demonstrated. They are inert in the dark under physiological conditions but become active as brominating reagents for tyrosine modification under visible light irradiation in the presence of a photocatalyst. The BODNs can be applied to protein labeling with bromo groups as sensitive mass tags. [ABSTRACT FROM AUTHOR]

Catalysis by chiral weakly‐coordinating anions (WCAs) remains underdeveloped due to the lack of a molecular design strategy for exploiting their characteristics, such as the non‐nucleophilic nature. Here, we report the development of a chiral borate ion comprising an O,N,N,O‐tetradentate backbone, which ensures hitherto unattainable structural robustness. Upon pairing with a proton, the hydrogen borate acts as an effective catalyst for the asymmetric Prins‐type cyclization of vinyl ethers, providing access to structurally and stereochemically defined dihydropyrans. The key to selectivity control is the distinct ability of the borate ion to discriminate the prochiral faces of the acyclic oxonium ion intermediate and dictate the regiochemical outcome. We anticipate that this study paves the way for exploring the untapped potential of WCA catalysis for selective chemical synthesis. [ABSTRACT FROM AUTHOR]

Catalysis by chiral weakly‐coordinating anions (WCAs) remains underdeveloped due to the lack of a molecular design strategy for exploiting their characteristics, such as the non‐nucleophilic nature. Here, we report the development of a chiral borate ion comprising an O,N,N,O‐tetradentate backbone, which ensures hitherto unattainable structural robustness. Upon pairing with a proton, the hydrogen borate acts as an effective catalyst for the asymmetric Prins‐type cyclization of vinyl ethers, providing access to structurally and stereochemically defined dihydropyrans. The key to selectivity control is the distinct ability of the borate ion to discriminate the prochiral faces of the acyclic oxonium ion intermediate and dictate the regiochemical outcome. We anticipate that this study paves the way for exploring the untapped potential of WCA catalysis for selective chemical synthesis. [ABSTRACT FROM AUTHOR]

Unlike carbonyl compounds, it has long been common understanding that excited imines show virtually no photoreactivity, and hence their properties and potential utility in chemical science remain largely unexplored. Now, a strategy is presented for eliciting latent photoreactivity of imines based on the introduction of a donor–acceptor (D‐A) structure to extend the lifetime of their photoexcited states. A series of spectroscopic analyses and density functional theory calculations reveal unique photophysical properties of the D‐A‐type imines. Furthermore, the reactivity of the D‐A‐type imines is demonstrated by using them as a photoredox catalyst for atom‐transfer radical addition. These findings illuminate a previously neglected chemical space in the field of photochemistry, which will be exploited by taking advantage of the inherent structural modularity of imines. [ABSTRACT FROM AUTHOR]

Unlike carbonyl compounds, it has long been common understanding that excited imines show virtually no photoreactivity, and hence their properties and potential utility in chemical science remain largely unexplored. Now, a strategy is presented for eliciting latent photoreactivity of imines based on the introduction of a donor–acceptor (D‐A) structure to extend the lifetime of their photoexcited states. A series of spectroscopic analyses and density functional theory calculations reveal unique photophysical properties of the D‐A‐type imines. Furthermore, the reactivity of the D‐A‐type imines is demonstrated by using them as a photoredox catalyst for atom‐transfer radical addition. These findings illuminate a previously neglected chemical space in the field of photochemistry, which will be exploited by taking advantage of the inherent structural modularity of imines. [ABSTRACT FROM AUTHOR]

Abstract: A site‐divergent stereoselective Michael reaction system is developed based on the identification of two distinct catalysts. Cinchonidine‐derived thiourea catalyzes the 1,4‐addition of prochiral azlactone enolates to enynyl N‐acyl pyrazoles in a highly diastereo‐ and enantioselective manner to give stereochemically defined alkynes, while P‐spiro chiral triaminoiminophosphorane catalytically controls the stereoselective 1,6‐addition and the consecutive γ‐protonation of the vinylogous enolate intermediate to afford Z,E‐configured conjugated dienes. This 1,6‐adduct serves as a valuable precursor for the synthesis of a 2‐amino‐2‐deoxy sugar. [ABSTRACT FROM AUTHOR]

Abstract: A site‐divergent stereoselective Michael reaction system is developed based on the identification of two distinct catalysts. Cinchonidine‐derived thiourea catalyzes the 1,4‐addition of prochiral azlactone enolates to enynyl N‐acyl pyrazoles in a highly diastereo‐ and enantioselective manner to give stereochemically defined alkynes, while P‐spiro chiral triaminoiminophosphorane catalytically controls the stereoselective 1,6‐addition and the consecutive γ‐protonation of the vinylogous enolate intermediate to afford Z,E‐configured conjugated dienes. This 1,6‐adduct serves as a valuable precursor for the synthesis of a 2‐amino‐2‐deoxy sugar. [ABSTRACT FROM AUTHOR]

We describe the design, synthesis, and characterization of a chiral hexacoordinated phosphate ion that features an octahedral P(V) core consisting of two N,N,O-tridentate backbones. We further demonstrate that the corresponding hydrogen phosphate acts as an effective catalyst for a highly enantioselective Pictet-Spengler-type reaction, wherein the relationship between the structure of the chiral phosphate ion and its ability to dictate the absolute stereochemistry is revealed in conjunction with precise structural elucidation of the phosphate ion. [ABSTRACT FROM AUTHOR]

The trifluoromethylation of enamines of ethyl 3-oxocarboxylates catalyzed by Fenton reagent with CF 3 I was investigated. Trifluoromethylation followed by acid hydrolysis provided 3-oxo-2-(trifluoromethyl)carboxylates in 64–94% yields, which were greater than those obtained by the trifluoromethylation of 3-oxocarboxylates as reported previously. Enamines trifluoromethylated at the 2-position were isolated as intermediates. Hydrolysis and successive decarboxylation of the obtained 3-oxo-2-(trifluoromethyl)carboxylates under acidic conditions provided (2,2,2-trifluoroethyl)ketones in satisfactory yields. [ABSTRACT FROM AUTHOR]

A highly E-selective and enantioselective conjugate addition of 2-benzyloxythiazol-5(4H)-ones to β-substituted alkynyl N-acyl pyrazoles is achieved under the catalysis of a P-spiro chiral iminophosphorane. Simultaneous control of the newly generated central chirality and olefin geometry is possible with a wide array of the alkynyl Michael acceptors possessing different aromatic and aliphatic β-substituents, as well as the various α-amino acid-derived thiazolone nucleophiles. This protocol provides access to structurally diverse, optically active α-amino acids bearing a geometrically defined trisubstituted olefinic component at the α-position. [ABSTRACT FROM AUTHOR]

A highly E-selective and enantioselective conjugate addition of 2-benzyloxythiazol-5(4H)-ones to β-substituted alkynyl N-acyl pyrazoles is achieved under the catalysis of a P-spiro chiral iminophosphorane. Simultaneous control of the newly generated central chirality and olefin geometry is possible with a wide array of the alkynyl Michael acceptors possessing different aromatic and aliphatic β-substituents, as well as the various α-amino acid-derived thiazolone nucleophiles. This protocol provides access to structurally diverse, optically active α-amino acids bearing a geometrically defined trisubstituted olefinic component at the α-position. [ABSTRACT FROM AUTHOR]

A highly stereoselective aza-Henry reaction of α-aryl nitromethanes with aromatic N-Boc imines was established by using C1-symmetric chiral ammonium betaine as a bifunctional organic base catalyst. Various substituted aryl groups for both imines and nitromethanes were tolerated in the reaction, and a series of precursors for the synthesis of unsymmetrical anti-1,2-diaryl ethylenediamines was provided. [ABSTRACT FROM AUTHOR]

Abstract: The studies on the development of a highly enantioselective oxidation of N-sulfonyl imines with hydrogen peroxide–trichloroacetonitrile system utilizing P-spiro chiral triaminoiminophosphoranes as an organic base catalyst are detailed. This method is general and scalable, and exhibits unique chemoselectivity, providing a practical stereoselective route to structurally diverse N-sulfonyl oxaziridines. The mechanistic investigations reveal that the reaction proceeds through the Payne-type oxidation pathway. The synthetic utility of the optically active N-sulfonyl oxaziridines as versatile organic oxidants and chiral building blocks is also demonstrated. [Copyright &y& Elsevier]

An efficient and highly enantioselective Payne-type oxidation of N-sulfonyl imines is developed. The reaction exhibits broad substrate generality and unique chemoselectivity based on the combined use of hydrogen peroxide and trichloroacetonitrile under the catalysis of P-spiro chiral trianilnoiminophosphorane. [ABSTRACT FROM AUTHOR]

A new strategy for developing stereoselective bond-forming reactions is introduced; it takes advantage of the ionic nucleophilic catalysis of chiral ammonium betaines to utilize vinylic esters simultaneously as the enolate precursor and the acylating agent for coupling with electrophiles. Its synthetic utility is clearly demonstrated by the realization of a highly diastereo- and enantioselective aldol reaction from oxindole-derived vinylic carbonates. [ABSTRACT FROM AUTHOR]

Abstract: Direct trifluoromethylation of 1,3-dicarbonyl compounds with CF3I in the presence of a Fenton reagent in dimethylsulfoxide was investigated. 1,3-Diketones, 3-oxocarboxylates and 3-oxocarboxamides were readily trifluoromethylated at the methylene carbon between two oxo groups. Cycloaddition of hydrazine derivatives to the obtained 2-(trifluoromethyl)-1,3-dicarbonyl compounds provided fluorinated pyrazoles. 4-(Trifluoromethyl)pyrazole derivatives were formed from 2-(trifluoromethyl)-1,3-diketones, while 3-oxo-2-(trifluoromethyl)carboxylates or carboxamides gave 5-fluoropyrazole-4-carboxylates or carboxamides, respectively, via 3-hydrazono-2-(trifluoromethyl)carboxylates or carboxamides as an intermediate. [Copyright &y& Elsevier]

Research to develop structurally discrete, chiral supramolecular catalysts for asymmetric organic transformations has met with limited success. Here, we report that a chiral tetraaminophosphonium cation, two phenols, and a phenoxide anion appear to self-assemble into a catalytically active supramolecular architecture through intermolecular hydrogen bonding. The structure of the resulting molecular assembly was determined in the solid state by means of x-ray diffraction analysis. Furthermore, in solution the complex promotes a highly stereoselective conjugate addition of acyl anion equivalents to α,β-unsaturated ester surrogates with a broad substrate scope. All structural components of the catalyst cooperatively participate in the stereocontrolling event. [ABSTRACT FROM AUTHOR]

Abstract: The Ni-catalyzed cross-coupling of 2-bromo-3,3,3-trifluoropropene and aryl Grignard reagents was investigated. When NiCl2(PPh3)2 was used as a catalyst, the highest yield of α-trifluoromethylstyrene (89%) from 2-bromo-3,3,3-trifluoropropene and PhMgBr was obtained in 1,3-dimethyl-2-imidazolidinone at 50°C for 30min. Various α-trifluoromethylstyrene derivatives could be produced in satisfactory yields by NiCl2(PPh3)2-catalyzed coupling using aryl Grignard reagents. [Copyright &y& Elsevier]

Abstract: Pd-catalyzed cross-coupling of 2-bromo-3,3,3-trifluoropropene (BTP) and arylmagnesium bromides was investigated. Diphenylphosphinomethane (dppm) was exclusively effective in the coupling among the phosphine ligands tested with Pd(0) and Pd(II) complexes. The use of diphenylphosphinomethane-coordinated Pd(II) complex, PdCl2(dppm), resulted in the highest yield of α-trifluoromethylstyrene (98%) from 2-bromo-3,3,3-trifluoropropene and phenylmagnesium bromide in 1,4-dioxane solvent at 50°C for 30min. The PdCl2(dppm)-catalyzed coupling could be applied to the synthesis of α-trifluoromethylstyrene derivatives with satisfactory yields using arylmagnesium bromides. [Copyright &y& Elsevier]

Abstract: The catalytic trifluoromethylation of uracil using CF3I was investigated to find a new industrial process for the production of 5-trifluoromethyluracil. The catalytic system of FeSO4, H2O2 and H2SO4 in dimethylsulfoxide efficiently and selectively yielded 5-trifluoromethyluracil under mild conditions. FeSO4 exhibited the highest activity among the Fe(II) compounds tested. H2O2 was indispensable for the reaction and only Fe(II) compounds yielded the desired product. This characteristic of the reaction suggests that it proceeds in a Fenton oxidation manner. The reaction was applicable to large-scale production: 50kg of 5-trifluoromethyluracil in a 600L reactor. By the use of this catalytic system, selective trifluoromethylation at the 5-position was also performed with various uracil derivatives including uridines. Interestingly, Cp2Fe was superior to FeSO4 for several substrates. [Copyright &y& Elsevier]

Abstract: Amination of S-methyl-N,N′-bis-Boc-isothiourea with either primary or sterically hindered secondary amines promoted by copper(I) chloride and K2CO3 gave N,N′-bis-Boc protected guanidines in good to excellent yields under mild reaction conditions. [Copyright &y& Elsevier]

An o -quinone methide (o -QM) competent as a catalyst for the dehydridative oxidation of benzylic alcohols was developed. The introduction of an overcrowded olefinic component into the o -QM induced structural distortion, beneficial for imparting triarylmethylium character and regenerability. The zwitterionc resonance form of the o -QM, generated via photoexcitation and subsequent relaxation, exerted the dehydridation activity. Density functional theory calculations were conducted to gain insights into the operative catalytic process. [Display omitted] [ABSTRACT FROM AUTHOR]

The vinylogous reactivity of α,β-disubstituted nitroolefins was uncovered through the facile generation of the corresponding α-substituted vinylogous nitronates and their use in the development of a highly diastereo- and enantioselective aza-Henry reaction with N-Boc aldimines under the catalysis of chiral ammonium betaines. The novel vinylogous nitronates undergo stereoselective bond formation at the sterically encumbered α-position exclusively, allowing the construction of contiguous tertiary–quaternary stereogenic carbon centers. [ABSTRACT FROM AUTHOR]

BINAM (1,1′-binaphthyl-2,2′-diamine)-derived bis -urea-catalyzed nucleophilic ring-opening of optically active and diastereomerically pure 2-EWG (electron-withdrawing group)-substituted N -(1-(1-naphthyl)ethyl)azetidinium salts with cesium fluoride in dichloromethane at room temperature proceeds at the less sterically hindered 4-position over the electronically deficient 2-position. Selective ring-opening at the 4-position is achieved by the combination of chiral stereocenters, as in N -(1-(1-naphthyl)ethyl)azetidinium salt, and steric bulk of the chiral bis -urea catalysts. The reaction affords the corresponding γ-fluoro-α-aminobutyric acid derivatives in diastereomerically pure. This protocol is applicable to the synthesis of enantiomerically enriched (98 % ee) γ-fluoro-α-amino acid derivatives starting from the commercially available chiral 1-(1-naphthyl)ethylamine. [Display omitted] • Synthesis of enantioenriched γ-fluoro-α-amino acids using CsF as a fluoride source. • Selective ring-opening of azetidinium salts with CsF and bis -urea catalyst. • Commercially available chiral 1-(1-naphthyl)ethylamine as a chiral source. [ABSTRACT FROM AUTHOR]

A two-step sequence for the asymmetric formal α-allylation of nitroalkanes is disclosed. This new methodology relies on the development of a highly diastereo- and enantioselective conjugate addition of nitroalkanes to vinylic 2-phenyl-1H-tetrazol-5-ylsulfones using chiral triaminoiminophosphorane as a requisite base catalyst and subsequent Julia–Kocienski olefination under kinetic conditions. [ABSTRACT FROM AUTHOR]

Chiral diaminodioxaphosphonium salts have been developed and their unique abilities as a chiral proton have been revealed through the establishment of a highly enantioselective protonation of α-amino acid-derived ketene disilyl acetals. [ABSTRACT FROM AUTHOR]

A C1-symmetric chiral ammonium betaine has been developed, and its intramolecular ion-pairing structure in solid state and its catalytic performance to achieve the highly stereoselective Mannich-type reaction of 2-alkoxythiazol-5(4H)-ones are revealed. [ABSTRACT FROM AUTHOR]

Highly enantioselective alkylation of azlactones derived from α-amino acids has been achieved under solid-liquid phase-transfer conditions using P-spiro chiral tetraaminophosphonium salt as a catalyst. The resulting alkylated azlactones can be readily converted into the corresponding α,α-disubstituted α-amino acids through simple acidic hydrolysis. [ABSTRACT FROM AUTHOR]

The parasitic plant Striga hermonthica has been causing devastating damage to the crop production in Africa. Because Striga requires host-generated strigolactones to germinate, the identification of selective and potent strigolactone agonists could help control these noxious weeds. We developed a selective agonist, sphynolactone-7, a hybrid molecule originated from chemical screening, that contains two functional modules derived from a synthetic scaffold and a core component of strigolactones. Cooperative action of these modules in the activation of a high-affinity strigolactone receptor ShHTL7 allows sphynolactone-7 to provoke Striga germination with potency in the femtomolar range. We demonstrate that sphynolactone-7 is effective for reducing Striga parasitism without impinging on host strigolactone-related processes [ABSTRACT FROM AUTHOR]

A divergent photocatalytic system for the reaction of α-bromo nitroalkanes with styrene derivatives is established, wherein the generation of the persistent nitroxyl radical as a junctional intermediate and suitable tuning of the redox ability of the system constitute the crucial elements for achieving rigorous control over the possible reaction pathways. [ABSTRACT FROM AUTHOR]

Scavengers that capture reactive chemical substances are used to prevent the decomposition of materials. However, in the field of catalysis, the development of scavengers that inhibit background pathways has attracted little attention, although the concept will open up an otherwise inaccessible reaction space. In catalytic bromination, fast non‐catalyzed background reactions disturb the catalytic control of the selectivity, even when using N‐bromoamide reagents, which have a milder reactivity than bromine (Br2). Here, we developed a trans‐cyclooctene (TCO) bearing a 2‐pyridylethyl group to efficiently retard background reactions by capturing Br2 in bromocyclization using N‐bromosuccinimide. The use of less than a stoichiometric amount of the TCO was sufficient to inhibit non‐catalyzed reactions, and mechanistic studies using the TCO revealed that in situ‐generated Br2 provides non‐catalyzed reaction pathways based on a chain mechanism. The TCO is useful as an additive for improving enantioselectivity and regioselectivity in catalytic reactions. Cooperative systems using the TCO with selective catalysts offer an alternative strategy for optimizing catalyst‐controlled selectivity during bromination. Moreover, it also served as an indicator of Br2 involved in catalytic reaction pathways; thus, the TCO was useful as a probe for mechanistic investigations into the involvement of Br2 in bromination reactions of interest. [ABSTRACT FROM AUTHOR]

Abstract: The catalytic performance of C 1-symmetric chiral ammonium betaines in the enantioselective direct Mannich-type reaction of α-nitrocarboxylates with N-Boc imines has been investigated. The most effective catalyst structure has been identified; this provides a reliable synthetic route to a variety of enantiomerically enriched α-tetrasubstituted α,β-diamino acid derivatives. [ABSTRACT FROM AUTHOR]

Trifluoromethylation followed by acid hydrolysis furnishes compounds (III) which can be converted to (2,2,2-trifluoroethyl)ketones via decarboxylation. [ABSTRACT FROM AUTHOR]

An abstract of the article "Synergistic Catalysis of Ionic Broensted Acid and Photosensitizer for a Redox Neutral Asymmetric alpha-Coupling of N-Arylaminomethanes with Aldimines" by D. Uraguchi, N. Kinoshita and T. Kizu is presented.

The article reports a study which uncovers a new function of chiral tetraaminophosphonium cations and its potential synthetic utility. According to the study, the heterochiral [7.7]-P-spirocyclic arylaminophosphonium barfates have been designed as a novel charged and cationic Brønsted acid catalyst. The study shows new functions of chiral aminophosphonium cations and that potential utility of asymmetric hydrogen-bonding catalysis is currently under close investigation.

The article offers information on chiral phosphonium dialkyl phosphite generation as chemical reagents. It notes that diakyl phosphonates are used for the asymmetric construction of phosphorus-carbon (P-C) bond in synthesizing chiral phosphonic acid derivatives. The relation of dialkyl phosphonates as P-nucleophile is affected by the concept of the phosphite tautomer. It also notes the creation of asymmetric catalysts of a chiral organic base for hydrophosphonylation of aldehydes.

The article presents a study which examines the asymmetric catalysis of chiral tetraaminophosphonium carboxylate. Its synthetic utility has been demonstrated by the application to the highly enantioselective direct Mannich-type reaction of azlactones with N-sulfonyl imines. The procedures employed in the experiment, as well as the observations and results of the study are also discussed,

The article describes the design of chiral quaternary ammonium betaines. The authors synthesized quaternary ammonium chloride as a precursor and examined an appropriate condition for the preparation of chiral ammonium betaine having an aryloxy moiety as a basic functionality. They evaluated the performance of betaines as a bifunctional organic base catalyst for asymmetric Mannich-type reaction of αnitrocarboxylates.

The article discusses a study on the chiral tetraaminophosphonium salt-mediated asymmetric direct Henry reaction. The study employed a chiral tetraaminophosphonium salt possessing the P-spirocyclic structure and its potential as an organic molecular catalyst. The development and application of a chiral tetraaminophosphonium chloride demonstrating its inherent potential to exert efficient asymetric catalysis. Researchers believe that this study offers a new axis of chiral onium salt catalyses.

This article focuses on organocatalytic asymmetric direct alkylation of α-diazoester via carbon-hydrogen bond cleavage. It has attracted much attention from industry as well as the academic community due to its atom efficiency. In conjunction with the recent efforts to develop chiral acids for catalyzed asymmetric carbon-carbon bond forming reactions, researchers recently demonstrated a highly enantio selective 1,2-aza-F-C reaction of a furan derivative to N-protected aldimines catalyzed by chiral phosphoric acid.

The article reports on the highly enantioselective 1,2-aza-Friedel-Crafts reaction catalyzed by a binaphthol mono-phosphoric acid. In view of the significance of controlling the stereochemistry in an absolute sense, the successful cultivation of a catalytic enantioselective variant of this reaction is in high demand. Since optically active furan-2-ylamines are highly useful synthetic building blocks, the article states the development of an enantioselective 1 ,2-aza-F-C reaction of a furan with N-Boc aldimine derivatives.

This article presents a study on the chiral Brønsted acid-catalyzation through direct Mannich reactions via electrophilic activation. It is a well-accepted that nearly a "proton"-like character is required for activating a substrate efficiently and hence chiral Brønsted acids could not provide a chiral environment to a reactive intermediate. Researchers have developed highly enantioselective Strecker reactions and Mannich reactions catalyzed by peptide-based thiourea derivatives as chiral Brønsted acids. Their achievement has clearly indicated that a chiral Brønsted acid could recognize enantiotopic faces of an imine substrate via hydrogen bonding and has opened up a new avenue in asymmetric catalysis.

Discusses the effect of rhodium-catalyzed allylic alkylation with an organozinc on the regio- and enantiospecific alkylation. Limitations of transition metal-catalyzed allylic substitution with unstabilized carbon nucleophiles; Description of the alkylation process of unsymmetrical allylic alcohol derivatives using aryl organozinc halides; Effectiveness of the Wilkinson's catalyst with organozinc reagents.

Various substituted aryl groups for both imines (I) and nitromethanes (II) are tolerated in the reaction. [ABSTRACT FROM AUTHOR]

Using a chiral iminophosphorane catalyst, the Michael addition between β-substituted alkynyl N-acyl pyrazoles and 2-benzyloxythiazol-5(4H)-ones proceeds with high yields and excellent stereo- and E/Z-selectivities. [ABSTRACT FROM AUTHOR]

The relief of the steric repulsion between cis-oriented substituents of the nitroolefins seems to assist the facile generation of the vinylogous nitronates, which react with N-Boc aldimines at the sterically more congested α-position exclusively, thus establishing the contiguous tertiary-quaternary stereocenters. [ABSTRACT FROM AUTHOR]

The article presents a chemical reaction of protonation of carboxylic acid-derived ketone by using the chiral ionic broensted acid catalysis.