Separation of Optically Active Ethynylsilane Derivatives and Their Polymerization by Transition-Metal Catalysts

Rhodium-catalyzed asymmetric synthesis of silicon-stereogenic silicon-bridged arylpyridinones

A rhodium-catalyzed regio- and enantioselective synthesis of silicon-stereogenic silicon-bridged arylpyridinones was developed. A reasonable catalytic cycle was also experimentally established.

A rhodium-catalyzed regio- and enantioselective synthesis of silicon-stereogenic silicon-bridged arylpyridinones has been developed through [2 + 2 + 2] cycloaddition of silicon-containing prochiral triynes with isocyanates. High yields and enantioselectivities have been achieved by employing an axially chiral monophosphine ligand, and this process could be applied to catalytic asymmetric synthesis of silicon-stereogenic chiral polymers for the first time. The reaction mechanism of the present catalysis has also been experimentally investigated to establish a reasonable catalytic cycle, advancing the mechanistic understanding of the rhodium-catalyzed pyridinone synthesis by [2 + 2 + 2] cycloaddition reactions.

Stereoselective Synthesis of Optically Active Disilanes and Selective Functionalization by the Cleavage of Silicon−Naphthyl Bonds with Bromine

Optically active disilanes with one chiral silicon center, (R)-1,2-dimethyl-1-(naphth-1-yl)-1,2,2-triphenyldisilane and (R)-1,2,2-trimethyl-2-(4-methoxynaphth-1-yl)-1-(naphth-1-yl)-1-phenyldisilane, were obtained by the reaction of (S)-methyl(naphth-1-yl)phenylchlorosilane (> 99% ee) with methyldiphenylsilyllithium or by the reaction of methyldiphenylchlorosilane with optically active (S)-methyl(naphth-1-yl)phenylsilyllithium and by the reaction of (S)-methyl(naphth-1-yl)phenylchlorosilane (> 99% ee) with dimethyl(4-methoxynaphth-1-yl)silyllithium. Under the optimized conditions, the reactions proceeded with almost complete inversion for the cholorosilanes and retention for the silyl anions. Optically active disilanes with two chiral centers, (1R,2R)-1,2-dimethyl-1,2-di(naphth-1-yl)-1,2-diphenyldisilane and (1S,2S)-1,2-di(4-methoxynaphth-1-yl)-1,2-dimethyl-1,2-diphenyldisilane, were obtained in high optical purity by the reactions of corresponding optically active halogenosilanes (Cl or F) with optically active silyllithiums. The silicon-silicon bond and the silicon-naphthyl bond of (R)-1,1,2-trimethyl-1,2-di(naphth-1-yl)-2-phenyldisilane and (1R,2R)-1,2-dimethyl-1,2-di(naphth-1-yl)-1,2-diphenyldisilane were cleaved without selectivity on bromination. The silicon-(4-methoxynaphth-1-yl) bond of (R)-1,2,2-trimethyl-2-(4-methoxynaphth-1-yl)-1-(naphth-1-yl)-1-phenyldisilane was regiospecifically cleaved, followed by the stereoselective cleavage of the remaining chiral silicon-naphthyl bond (94% inversion). Although the silicon-(4-methoxynaphth-1-yl) bonds of (1S,2S)-1,2-di(4-methoxynaphth-1-yl)-1,2-dimethyl-1,2-diphenyldisilane (> 99% ee) were regioselectively cleaved without silicon-silicon bond scission, remarkable racemization could not be avoided during the one-pot reaction.