Palladium-catalyzed asymmetric hydrogenation of lactones under base-free conditions.

Asymmetric hydrogenation of esters through homogeneous catalysis is a significantly important transformation in organic synthesis. The systems developed so far mainly focused on chiral iridium and ruthenium catalysts, which required a base to facilitate the activity. Herein, we present a palladium-catalyzed asymmetric hydrogenation of lactones under base-free conditions through dynamic kinetic resolution and kinetic resolution. The reaction exhibits high enantioselectivity and excellent functional group tolerance. Remarkably, the hydrogenation proceeds smoothly at the gram scale, and the products can be transformed into several chiral potential building blocks without loss of optical purity. This work provides a new strategy for asymmetric hydrogenation of esters under base-free conditions.

Diarylborinic Acid-Catalyzed Ring Opening of cis-4-Hydroxymethyl-1,2-Cyclopentene Oxides: Synthesis of 1,2,4-Trisubstituted Cyclopentanes.

A diarylborinic acid-catalyzed ring opening of cis-4-hydroxymethyl-1,2-cyclopentene oxides was developed with N-nucleophiles including anilines, benzotriazole, and alkylamines, as well as S-nucleophiles, affording 1,2,4-trisubstituted cyclopentane compounds containing a quaternary carbon center. The mechanism study indicated that the "half-cage" structure formed by the epoxide substrate and the catalyst prevents the nucleophiles from attacking the inner side of the "half-cage", resulting in the desired ring-opening product.