Diazo Strategy for Intramolecular Azirine Ring Expansion: Rh(II)- Catalyzed Synthesis of 2-Hydroxy-3-oxo-2,3-dihydro-1H-pyrrole-2-carboxylates

A diazo strategy for the intramolecular azirine ring expansion was developed. Azirinyl-substituted diazodicarbonyl compounds, prepared from diazoacetylazirines, were converted in excellent yields to 2-hydroxy-3-oxo-2,3-dihydro-1H-pyrrole-2-carboxylates under Rh catalysis in the presence of water. According to DFT calculations, the formation of only pyrrolinone derivatives and the absence of O-H insertion products of Rh carbene into water are due to the low Gibbs free energy of the transition state for the concerted opening of the azirine ring and recyclization to pyrrolone in intermediate Rh complexes.

Automated summary

A diazo strategy for intramolecular azirine ring expansion was developed. Azirinyl-substituted diazodicarbonyl compounds, prepared from diazoacetylazirines, were efficiently converted to 2-hydroxy-3-oxo-2,3-dihydro-1H-pyrrole-2-carboxylates under Rh catalysis and in the presence of water. The formation of only pyrrolinone derivatives and the absence of O-H insertion products of Rh carbene into water can be attributed to the low Gibbs free energy of the transition state for the concerted opening of the azirine ring and recyclization to pyrrolone in intermediate Rh complexes.