Regiospecific silylation of 2,5-dibromothiophene: a reinvestigation

Lithiation of 2,5-dibromothiophene by LDA with ensuing silylation proceeds regiospecifically in accordance with the halogen dance mechanism to yield 3 ,5-dibromo-2-trimethylsilylthiophene or 3,4-dibromo-2,5-bis(trimethylsilyl) thiophene depending on the ratio of reagents. The outcome of the reaction w as confirmed by further chemical transformations of the latter compound to 2,5-bis(trimethylsilyl)thiophene and 2,5-bis(trimethylsilyl)thiophene-1,1-d ioxide. The structures of the compounds obtained were determined by H-1, C- 13 and Si-29 NMR, and X-ray analysis in the case of a sulfone. (C) 2001 Els evier Science Ltd. All rights reserved.