CYCLOADDITION OF β-SUBSTITUTED ENONES TO A BICYCLICSYDNONE: OBSERVATION OF AN UNEXPECTED FACILE HYDROCARBON ELIMINATION
Cycloaddition of β-alkyl or β-arylenones to bicyclic sydnone 3 in the absence of added oxidant affords mixtures of the tetrahydropyrazolopyridines 4 and 5.The amount of 5 formed was dependent on the nature of R.