Concise design and synthesis of pyridine-fused heterocycles via 6 pi- Azaelectrocyclization process of iminoalkyne derivatives

A concise and regioselective approach to the synthesis of pyridine-fused heterocycles and benzoxazepine derivatives was developed. Propargyl imines derived from aromatic aldehydes and propargyl amine underwent 6 pi-electrocyclization reactions at high temperatures in high yields to form pyridine-fused heterocycles. Application of the same methodology to aromatic imines having a hydroxyl group in the ortho position resulted in the formation of (benz)oxazepine derivatives. The formation mechanism of the products was discussed. (C) 2019 Elsevier Ltd. All rights reserved.