Reactions of phenyldimethylsilyllithium with beta-N,N-dimethylaminoenones

Phenyldimethylsilyllithium reacts with the (beta)-N,N-dimethylaminoenones 1 and 7, with the enal 5, and with ethyl (beta)-N,Ndimethylaminoacrylate 9 to give the corresponding (beta),(beta)-unsaturated carbonyl compounds with a (beta)-phenyldimethylsilyl group, but in the last case only when the reaction mixture is given a mysteriously brief treatment with methyl iodide before workup.