Chromium(II)-mediated synthesis of vinylbis(silanes) from aldehydes and a study of acid- and base-induced reactions of the derived epoxybis(silanes): a synthesis of acylsilanes

The synthesis of vinylbis(silanes) 1 from aldehydes and dibromomethylenebis(trimethylsilane) using chromium(II) chloride in DMF is described. Epoxidation of vinylbis(silanes) 1 and treatment of the resulting epoxybis(silanes) 2 with sulfuric acid in methanol gives acylsilanes 3. Mechanistic studies of acylsilane formation, together with a crystal structure of epoxybis(silane)2 (R=3,5-dinitrobenzoyloxymethyl) and the finding that 1-halovinylsilanes 7 (X=Cl, Br, I) can be prepared from epoxybis(silanes) 2 using hydrogen halides, all indicate that the preferred site of nucleophilic attack in epoxybis(silanes)2 is at the disilyl-substituted carbon. Reaction of alkyl-substituted epoxybis(silanes) such as 2b,c with LDA proceeds by an unusual rearrangement process to give silanols 14.