Abstract The decomposition of diazo ester 2b with chiral Rh II catalysts proceeded via intramolecular aromatic carbenoid insertion to the racemic pyrrole derivative 5b in 72% yield. In contrast, the benzoylated precursor 16 afforded no ketorolac 1b when exposed to Rh II. Methyl 2-diazo-4-phenylbutyrate (19), in turn, reacted, by 1, 2-hydrogen migration rather than by aromatic substitution, to 20.