N-Heterocyclic carbene-catalyzed [2+3] cyclocondensation of α-chloroaldehydes with azomethine iminesElectronic supplementary information (ESI) available: Experimental procedures and spectroscopic data. CCDC 1048523 for compound 3k. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5cc01238d

An N-heterocyclic carbene-catalyzed enantioselective [2+3] cyclocondensation of α-chloroaldehydes with azomethine imines was developed. The corresponding pyrazolidinones were obtained in good yields with moderate to good diastereoselectivities and excellent enantioselectivities. The N-heterocyclic carbene-catalyzed enantioselective [2+3] cyclocondensation of α-chloroaldehydes with azomethine imines was developed to give the corresponding pyrazolidinones in good yields with excellent enantioselectivities.