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.