Regioselective Anti -Silyllithiation of Propargylic Alcohols.

Among the known hydrosilylation or carbosilylation conditions of alkynes, anti -addition of the two units across the triple bond is considered rare compared to the syn counterpart. For anti -silylative vicinal difunctionalizations, transition-metal catalysts, such as ruthenium or palladium complexes, are generally required. Accordingly, silyl alkali metals have not been employed for those anti -addition transformations. Here we demonstrate that silyllithiums can add across the triple bond of a series of propargylic alkoxides regioselectively in an anti -fashion. Upon treatment with a variety of electrophiles, the trisubstituted alkenyl lithium intermediates were transformed into highly functionalized β-silyl allylic alcohols with high regiocontrol, eventually providing tri- or tetrasubstituted alkenylsilanes stereoselectively. A classic trick for anti -addition with propargylic alkoxides has transformed anti -silylative functionalizations into a robust and reliable strategy.