A [4+3] Cycloaddition Reaction of Aza-ortho-quinone Methides with C,N-Cyclic Azomethine Imines for Synthesis of 1,2,4-Triazepines

Abstract The base-induced formal [4+3] cycloaddition reaction of C,N-cyclic azomethine imines with aza-ortho-quinone methides, generated in situ, is reported. This protocol provided an efficient method for the synthesis of biologically important 1,2,4-triazepine derivatives, with a wide substrate scope and excellent functional-group tolerance, and it gives moderate to excellent yields under mild conditions. Several of the derivatives exhibited in vitro antitumor activities against the A2780 cell line in a screening of the cancer cell lines HCT-116, H2228, and A2780 by an MTT assay.