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Short Paper | Regular issue | Vol 94, No. 2, 2017, pp.342-349
Published online, 27th January, 2017
DOI: 10.3987/COM-16-13632
Facile and Short-Step Synthesis of 5-Substituted 2,3,4,5-Tetrahydrobenz[f][1,4]Oxazepines Using a Modified Pictet-spengler Reaction

Toshiaki Saitoh, Michikazu Kitabatake, Takuya Sugimoto, Hiromu Kawakubo, Kunihiko Mohri, and Yoshie Horiguchi*

*Faculty of Pharmaceutical Sciences, Showa Pharmaceutical University, 3-3165, Higashi-tamagawagakuen, Machida, Tokyo 194-8543, Japan

Abstract

5-Substituted 2,3,4,5-tetrahydrobenzo[f][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.