NOVEL ROUTE TO C=SI DOUBLE-BONDS VIA A PETERSON-TYPE REACTION

Reaction of (Me3Si)3SiLi.3THF (1) with adamantanone in hexane or benzene leads via a Peterson-type elimination reaction to the silene bis(trimethylsilyl)-adamantylidenesilane (3), which spontaneously dimerizes in a head-to-head fashion (80-90% yield) to 1, 1,2,2-tetrakis(trimethylsilyl) dispiro[3,3',4,4'-biadamantane-1,2-disilacyclobutane] (2). When it is warmed, 2 reverts to 3, which was trapped by 1-methoxybutadiene or methanol. The X-ray structure of 2 is reported. The four-membered ring is strongly puckered and has unusually long C-C and C-Si bond lengths of 1.647 and 2.008 angstrom, respectively. Reaction of 1 with 4-tert-butylcyclohexanone also proceeds via the corresponding silene, which dimerizes to 1, 1,2,2-tetrakis(trimethylsilyl)-1-(4-tert-butylcyclohexyl)-2-(4-tert-butylcyclohexenyl)disilane.