A new synthesis of azocines

Abstract

Methyl and ethyl 7,8-diphenylazocine-2-carboxylate have been prepared by the reaction of dimethyl tricyclo[4,2,2,0^2,5]deca-3,7,9-triene-7,8-dicarboxylate with methyl or ethyl 5,6-diphenyl-1,2,4-triazine-3-carboxylate. The flexibility of this azocine ring system has been studied by p.m.r. spectroscopy and it was found that a higher temperature was required to effect rapid ring inversion in this case, in comparison with the related cyclooctatetraenes. A related bridged dihydroazocine (8) has been synthesized by the [π2s + π4s] cycloaddition of dimethyl tricyclo-[4,2,2,0^2,5]deca-3,9-diene-7,8-dicarboxylate to ethyl 5,6-diphenyl-1,2,4-triazine-3-car-boxylate. In contrast to previously described dihydroazocines, this compound exists entirely in the monocyclic form. Other [π2s + π4s] cycloadditions have also been described in which the π4s component was part of a triazine or a 3-azabicyclo-[4,2,0]octa-2,4-diene ring system.