FACILE AND SHORT-STEP SYNTHESIS OF 5-SUBSTITUTED 2,3,4,5-TETRAHYDROBENZO[f][1,4]OXAZEPINES USING A MODIFIED PICTET-SPENGLER REACTION

摘要

5-Substituted 2,3,4,5-tetrahydrobenzo [1,4] oxazepines (6) were synthesized using a modified Pictet-Spengler reaction of formyliminium ion (4) as the key step. Cyclization of 4 proceeded readily by using trifluoroacetic acid as a catalyst, giving 5 -substituted N-formyl-2,3,4,5-tetrahydrobenzo[f][1,4]oxazepines (5) in 26-78% yield. The imination of 2-phenoxyethanamine (1) with aldehydes, formylation of the resulting imines (3), and the acid-catalyzed cyclization steps could be carried out in a one-pot procedure. Hydrolysis of 5 with hydrochloric acid gave the 5-substituted 2,3,4,5-tetrahydrobenzo[f][1,4]oxazepines (6) in high yields.