Reactions of Decaborane(14) with Silylated Acetylenes. Synthesis of the New Monocarbon Carborane 9-Me2S-7-((Me3Si)2CH)-CB10H11

摘要

The reaction of decarboranes(14) with an alkyne in the presence of dimethyl sulfide is a well-established route to ortho-carborane 1,2-C2B10H12 and its alkyl derivatives. Previous studies have suggested that this reaction involves the initial formation of bis(dimethyl sulfide) decaborane, which can then dissociate a dimethyl sulfide, yielding a reactive B10H12SMe2 species. Further reaction of this B10H12SMe2 intermediate with the alkyne then leads to the direct insertion of the two-carbon acetylenic unit into the cage along with dissociation of the remaining SMe2 and H2 loss to yield the final product. We have now investigated the dimethyl sulfide promoted reactions of decaborane with two silylated acetylenes, bis(trimethylsilyl) acetylene and (trimethylsilyl) propyne, and report that, in contrast to the results discussed above, these reactions do not result in the formation of ortho-carborane derivatives. Instead, hydroboration of the acetylene, accompanied by silyl group migration is observed in both cases to yield as major products 5-(dimethyl sulfide)-6-alkenyldecaborne compounds.