The dipolar cycloaddition of methyl acrylate to 5,6-diethyl-1-methyl-3- oxidopyrazinium

Abstract

5,6-Diethylpyrazin-2-one reacts with iodomethane to give a quaternary salt, deprotonation of which, in situ, liberates a 3-oxidopyrazinium which undergoes a 1,3-dipolar cycloaddition with methyl acrylate to form methyl (Z)-5-ethyl-4-ethylidene-8-methyl-2-oxo-3,8-diazabicyclo[3.2.1] octane-6-endo-6-carboxylate. The crystal structure revealed (i) the existence of the imine product as its enamine tautomer, (ii) the Z geometry of the exocyclic double bond, and (iii) the endo orientation of the ester group. Pairwise hydrogen bonding between the NH H atom and the amide carbonyl group links the molecules into centrosymmetric dimers. © 2006 International Union of Crystallography. All rights reserved.