Insights into the role played by modified cinchona alkaloids in the Sharpless asymmetric dihydroxylation inspired studies of modified cinchona alkaloids as chiral organic catalysts that lead to the development of highly enantioselective alcoholyses for the desymmetrization, kinetic resolution, and dynamic kinetic resolution of cyclic anhydrides, cyanation of ketones, and 1,4-addition of thiols to cylic enones. These studies demonstrate the potential of modified cinchona alkaloids as broadly useful chiral organic catalysts for asymmetric synthesis.

Scheme 2. Proposed reaction pathways for the iodine-catalyzed sulfenylation of indoles with sulfonyl hydrazides. Scheme 3. Proposed reaction pathways for the iodine-promoted decomposition of sulfonyl hydrazides. Angewandte Chemie 4931

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The development of broadly applicable and practical catalytic approaches for the enantioselective creation of quaternary stereocenters remains a highly desirable yet challenging goal. In this Communication, we describe a highly enantioselective cyanosilylation of acetal ketones (alpha,alpha-dialkoxy ketones) catalyzed by modified cinchona alkaloids. This reaction is the first highly enantioselective cyanosilylation of ketones catalyzed by an organic chiral Lewis base and is found to be highly efficient with acetal ketones bearing a broad range of alkyl, aryl, alkenyl, and alkynyl substituents. This new catalytic asymmetric reaction, coupled with the versatility of the acetal functionality, provides a broadly useful synthetic method for chiral building blocks bearing quaternary stereocenters. Acetal ketones, readily accessible but previously unexplored in asymmetric synthesis, demonstrate unusual reactivity and selectivity toward the nucleophilic cyanosilylation, thereby suggesting that they may be interesting substrates for other catalytic enantioselective reactions.

The Wittig reaction involving direct olefination of triphenylphosphonium ylides (Ph(3)P horizontal lineCHR) with aldehydes is arguably the most often used method for alkene synthesis, but in general it yields mixtures of Z- and E-alkenes for semistabilized triphenylphosphonium ylides (R = aryl or vinyl). We have developed a simple and efficient protocol to improve the stereoselectivity significantly by replacing the aldehydes used in the Wittig reaction with N-sulfonyl imines, which possess distinct electronic and steric properties relative to aldehydes. A broad range of aromatic, alpha,beta-unsaturated, and aliphatic imines bearing appropriate N-sulfonyl groups smoothly undergo olefination reaction with various benzylidenetriphenylphosphoranes or allylidenetriphenylphosphoranes under mild reaction conditions to afford an array of both Z- and E-isomers of conjugated alkenes in good to excellent yields and with greater than 99:1 stereoselectivity. Moreover, this tunable protocol has been successfully applied to the highly stereoselective synthesis of two anticancer agents, DMU-212 and its Z-isomer.

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A new nanocluster of atomic precision, Au44(SC2H4Ph)32, is obtained by an oxidation-decomposition-recombination (ODR) process from Au25(SC2H4Ph)18 under mild conditions with high yield (75%). Among the investigated gold nanoclusters, Au44(SC2H4Ph)32 exhibits the highest catalytic activity for the reduction of 4-nitrophenol, especially at low temperature, indicating that the catalytic properties of gold nanoclusters are not only size-dependent, but also structure-sensitive.

A useful source: Arylsulfonyl hydrazides have been identified as synthetically useful aryl sources for the Pd(OAc)2 catalyzed oxidative Mizoroki–Heck‐type reaction under molecular oxygen to provide a convenient access to polysubstituted alkenes in a highly regio‐ and stereoselective manner (see scheme). The reaction well tolerates various functional groups such as alkoxy, halo, alcohol, carboxylic acid, ester, amide, sulfonamide, and sulfone.