SELECTIVITY IN THE REACTIONS OF ALKYLLITHIUM REAGENTS WITH α, ω-DICHLOROPERMETHYLSILOXANES

Article abstract of DOI:10.1016/0022-328X(83)89525-4

The reactions of 1,3-dichlorotetramethyldisiloxane and 1,5-dichlorohexamethyltrisiloxane with alkyllithium reagents have been studied.At low temperature (-78 deg C) only one of the two silicon-chlorine bonds of 1,3-dichlorotetramethyldisiloxane reacts readily with alkyllithium reagents.This permits the selective preparation of 1-alkyl-3-chlorotetramethyldisiloxanes or by hydrolysis 1-alkyl-3-hydroxytetramethyldisoloxanes.The silicon-chlorine bond of 1-alkyl-3-chlorotetramethyldisiloxanes reacts with alkyllithium reagents at higher temperatures (0 deg C).Both the silicon-chlorine bonds of 1,5-dichlorohexamethyltrisiloxane react competitively with alkyllithium reagents at -78 deg C.No cleavage of siloxane bonds by alkyllithium reagents is observed under these conditions.Spectral properties of a number of 1-alkyl-3-hydroxytetramethyldisiloxane and 1-alkyl-5-hydroxyhexamethyltrisoloxanes are reported.