SILYLAMINES IN ORGANIC-SYNTHESIS - REACTIVITY OF N,N-BIS(SILYL) ENAMINES TOWARD ELECTROPHILES - A ROUTE TO SUBSTITUTED 2-AZA-1,3-BUTADIENES AND PYRIDINES

Nfl-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 a,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. © 1990, American Chemical Society. All rights reserved.