Ring Opening of Epoxides by Pendant Silanols.

We present a new ring-opening reaction of epoxides by pendant silanols, catalyzed by either Ph 3 C + BF 4 - or BINOL-phosphoric acid. Silanol epoxides derived from trans -allylic alcohols, cis -allylic alcohols, trans -homoallylic alcohols, and cis -homoallylic alcohols were all compatible and gave products from either endo - or exo -ring opening. With silanol epoxides derived from 4-alkenyl silanols, an unusual rearrangement to tetrahydrofuran products was observed. The utility of this methodology was demonstrated in a short preparation of protected d-arabitol.