The catalytic asymmetric halohydroxylation of α,β‐unsaturated ketones with water as the nucleophile has been realized by applying a chiral N,N′‐dioxide/Fe(OTf)2 complex as the catalyst. Bromo‐, chloro‐ and iodo‐hydroxylations were all suitable in this catalytic system. A variety of α‐halo‐β‐hydroxy ketones were obtained in often good yields with generally high dr and ee values. Besides, a Michael/α‐halogenation process was considered more possible and a possible transition state model was proposed to explain the origin of stereoselectivity.magnified image

Catalytic asymmetric synthesis of hydrothiazole derivatives was developed via a well-organized formal [2 + 1 + 2] cycloaddition reaction triggered by asymmetric addition of isocyanide to alkylidene malonate. Various chiral hydrothiazole derivatives were readily provided in good yield with high enantioselectivity (up to 98% yield, 98.5:1.5 er) utilizing a chiral Mg­(OTf)2/N,N′-dioxide complex as the catalyst under mild conditions. Based on the experimental studies and the structure of the catalyst, a possible catalytic cycle was proposed to elucidate the reaction process and activation mode.

A unique chiral amine organocatalyst with a bispidine structure was found to be efficient for the diastereo- and enantioselective Mannich reaction of isatin ketimines with ketones. A series of 3-substituted 3-amino-2-oxindoles bearing vicinal tertiary and quaternary chiral stereogenic centers were obtained in excellent yields with excellent dr and ee values. The gram-scale synthesis and transformation of the product showed the practicability of this methodology. In addition, a possible transition state model was proposed to explain the origin of the stereoselectivity.

Tuning diastereoselectivity is a great challenge in asymmetric catalysis for the inherent stereochemical bias of the substrates. Here, we report a diastereodivergent asymmetric Mannich reaction of cyclic N-sulfonyl ketimines with...

This article first provides an algorithm W based type inference algorithm for an affine type system. Then the article further assumes the language equipped with the above type system uses lazy evaluation, and explores the possibility of representing the !-modality as a user-defined type synonym with the power of the newly gained polymorphism.