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 la,b, with a variety of electrophiles 3 is investigated, The reaction with bulky and/or hard silyl chlorides, such as Bu'Me(2)SiCl, (Pr3SiCl)-Si-i, (Thexyl)Me(2)SiCl and Bu'Ph(2)SiCl, 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 Me(3)SiCl, 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.