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(Ot-Bu) 2(OMe) 2 and Si(Ot-Bu)(OMe) 3 selectively gives trimer (MeO) 2Si[OSiMe(OMe) 2] 2 and dimer (MeO) 3SiOSiMe(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.
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