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,N-dimethylaminoacrylate 9 to give the corresponding alpha,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.