N-Substituted and N-unsubstituted 1,3-Oxazolium-5-olates cycloaddition reactions with 3-substituted coumarins

The 1,3-dipolar cycloaddition reaction of unsymmetrically N-substituted and N-unsubstituted 1,3-oxazolium-5-olates with selected 3-substituted coumarins has been examined. Various types of pyrrole derivatives are isolated and their formation seems to be a function of the regio- and diastereochemistry of the initial cycloaddition step.