Direct alkoxysilylation of alkoxysilanes for the synthesis of explicit alkoxysiloxane oligomers

Abstract Direct alkoxysilylation, which is a powerful tool to provide explicit alkoxysiloxanes, is developed and its versatility is investigated. Siloxane pentamers Si[OSiR 1 (OMe) 2 ] 4 having various functional groups (R 1  = methyl, vinyl, phenyl, chloropropyl and n -butyl groups) were successfully obtained by direct alkoxysilylation of Si(OR) 4 (R =  t -Bu, CHPh 2 ). Thus, the versatility of the reaction is confirmed on organic functional groups R 1 . Functional group tolerance of the reaction is discussed on the basis of electronegativity of the R 1 groups. Alkoxysilylation of Si(O t -Bu) 2 (OMe) 2 and Si(O t -Bu)(OMe) 3 selectively gives trimer (MeO) 2 Si[OSiMe(OMe) 2 ] 2 and dimer (MeO) 3 SiOSiMe(OMe) 2 , respectively. Thus, the feasibility on siloxane structure is also confirmed. Various siloxane compounds are synthesized by this newly developed reaction for the first time.