A series of N-acyl 2-diazo-3-oxobutanoates, when treated with a catalytic quantity of a rhodium (II) carboxylate, were found to afford substituted pyrroles derived from an azomethine ylide intermediate. The initial reaction involves generation of the expected carbonyl ylide dipole by intramolecular cyclization of the keto carbenoid onto the oxygen atom of the neighboring amide group. The primary cycloadduct undergoes a subsequent ...
