Acta Cryst. (2006). E62, o2318-o2320  [ doi:10.1107/S1600536806017107 ]

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

M. Helliwell, Y. You and J. A. Joule

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.

Online 12 May 2006

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