Reaction of ynolate anions derived from silylketenes with electrophiles: a facile preparation of silyl ynol ethers and functionalized silylketenes

Reaction of the ynolate anions 2a,b, generated from the silylketenes 1a,b, with a variety of electrophiles 3 is investigated. The reaction with bulky and/or hard silyl chlorides, such as ButMe2SiCl, PriSiCl, (Thexyl)Me2SiCl and ButPh2SiCl, exclusively gives the silyl ynol ethers 4, while that with small or soft silyl chlorides and stannyl chlorides gives only the functionalized silylketenes 5 in modest to high yields, respectively. In the case of the reaction with small and hard Me3SiCl, initial formation of the O-trimethylsilyl ynol ether 4b and the subsequent rapid isomerization to the bis-silylketene 5a are proposed by the trapping of 4b as a cobalt complex 7b.