Ketenimines bearing electron-withdrawing groups (X in 1) at the C2-position react with lithium trimethylsilyldiazomethanide [diazo (lithio) trimethylsilylmethane] to give 4-amino-3- trimethylsilylpyrazoles 4 or 5 mainly; in some cases 4-trimethylsilyl-1, 2, 3-triazole derivatives 3 were formed as the major products.
