UNEXPECTED BEHAVIOR OF SILOLES TOWARD ORGANOLITHIUM REAGENTS

Article abstract of DOI:10.1016/S0022-328X(00)86110-0

The reaction of 5-trimethylsilyl-5-methyldibenzosilole (I) with an excess of methyllithium in THF afforded 5,5-dimethyldibenzosilole (II) in quantitative yield.Treatment of I with an excess of butyllithium gave 5,5-dibutyldibenzosilole (III) quantitatively.Similar treatment of II with butyllithium in THF at room temperature gave III in almost quantitative yield, while treatment of III with methyllithium at reflux temperature gave II and 5-butyl-5-methyldibenzosilole in 10 and 40percent yield, in addition to 37percent of the starting III. 1,2,5-Tris(trimethylsilyl)-1-methyl-3,4-diphenylsilole also reacted with methyllithium to give 1,1-dimethyl-2,2,5-tris(trimethylsilyl)-3,4-diphenyl-1-silacyclopent-3-ene and 1,1-dimethyl-2,5-bis(trimethylsilyl)-3,4-diphenylsilole in 70 and 7percent yield.A five-coordinate silicon compound is proposed as an intermediate.