Reactions of pyrazolium salts with silyllithium reagents. Regioselective synthesis of 5-silylated 3-pyrazolines

Article abstract of DOI:10.1016/S0040-4039(97)10825-5

1,3,5-trisubstituted-2-methylpyrazolium iodides react with dimethylphenylsilyl- and tert-butyldiphenylsilyllithium leading, in general, to one of the corresponding 5-silyl-3-pyrazolines. The silyl group is easily substituted by electrophiles to give 5-functionalized 3-pyrazolines. Moreover, 5-silyl-3-pyrazolines undergo thermic ring opening with silicon-rearrangement affording α-silylated β-diimines.