An unusual furan cycloadduct from N-phenylbetaine and dimethyl acetylenedicarboxylate. The crystal and molecular structure of dimethyl 5-(3-N-phenyliminoprop-1-enyl)furan-2,3-dicarboxylate
Abstract
Cycloaddition of dimethyl acetylenedicarboxylate with betaines such as 1-phenyl-3-oxidopyridinium does not yield the expected bicyclic product; instead, addition occurs at the exocyclic oxygen atom and ring carbon 2 of the betaine, with concomitant opening of the pyridine ring.