Chemistry of Silylketenes

Reaction of silylketenes 1a, b with stabilized ylides 2a-e readily gave silylallenes 3a-f in high yields. However, similar reaction of 1a with the less stable ylides 2f, g resulted in low yields of the allenes 3 g, h. Use of silylketenes 5a, c with an additional trimethylsilyl group overcame this problem to give silylallenes 3c, g-k directly in considerable to good yields. In this reaction, the additional trimethylsilyl group apparently worked as a masking group.