Silylamines in Organic Synthesis. Reactivity of N,N-Bis(silyl) Enamines toward Electrophiles. A Route to Substituted 2-Aza-1,3-butadienes and Pyridines

Article abstract of DOI:10.1021/jo00296a059

N,N-Bis(silyl) enamines appeared to be weak nucleophilic reagents and exhibited a very low reactivity toward electrophiles.However, in the presence of a nucleophilic catalyst, nucleophilic activation of the silicon-nitrogen bond was observed.Under fluoride ion catalysis (TBAF or CsF), N,N-bis(silyl) enamines reacted with carbonyl compounds to give substituted 2-aza-1,3-butadienes.Good yields were obtained in reactions with aromatic aldehydes or ketones.In the case of aliphatic carbonyl compounds, 2-aza 1,3-dienes were only formed in moderate yields.Interestingly, enamidines were easily obtained in high yields upon reactions of dimethylformamide in the presence of MeONa as catalyst.The reaction of aromatic α,β-unsaturated ketones gave 2-aza 1,3,5-trienes, which were not isolated but underwent an intramolecular cycloaddition reaction with regioselective formation of substituted 2,4-diarylpyridines.