Synthesis of 4-Quinolones: N,O-Bis(trimethylsilyl)acetamide-Mediated Cyclization with Cleavage of Aromatic C-O Bond

摘要

The synthesis of 1,4-dihydro-4-oxoquinoline derivatives (4-quinolones) based on a BSA [N,O-bis(trimethylsilyl)acetamide]-mediated cyclization of substituted 1-(2-methoxyphenyl)-3-(alkyl/arylamino)prop-2-en-1-ones is described. The reaction belongs to a rare set of cyclizations in which a methoxy group serves as the leaving group. Reaction takes place by the action of silylating agent under mild conditions and provides high yields of pure products following simple aqueous work-up. The versatility of the approach is exemplified by a wide range of 1-alkyl/aryl 3-carboxylates and 3-nitriles that have been prepared. A crucial advantage of this approach is the facile availability of starting methoxy compounds enabling new synthetic possibilities as well as improved cost efficiency.