A new method for the synthesis of 2-cyclopenten-1-one-5-carboxylic ester derivatives via Rh2(OAc)4-mediated intramolecular C–H insertion reaction of 4Z-β-vinyl-α-diazo β-ketoesters

2-Cyclopenten-1-one-5-carboxylic ester derivatives are synthesized in a four-step-reaction sequence starting from alkynyl aldehydes via 4Z-β-vinyl-α-diazo β-ketoesters intermediate . The synthetic method for is described. When the δ substituent is an alkyl group, Rh(II)-mediated decomposition of the diazo compounds led to an intramolecular C–H insertion to afford 2-cyclopenten-1-one-5-carboxylic ester derivatives in high yields. When the δ substituent is an aryl group, 2-hydroxynaphthoate is obtained exclusively. In both cases, no Wolff rearrangement product was observed.