An unusual by-product from a non-synchronous reaction between ethyl 1,2,4-triazine-3-carboxylate and an enamine

Abstract

The main product from the reaction of ethyl 1,2,4-triazine-3-carboxylate 3 and the pyrrolidine enamine of N-tert-butoxycarbonylpiperidone 2 was an azabicyclo[3.2.1]octane 4 which resulted not from a Diels–Alder reaction, but from a series of non-synchronous steps, demonstrating a heretofore unknown reaction pathway for the electron-deficient diene 3 and electron-rich dienophile 2.