Diastereoselective construction of cyclopent-2-enone-4-ols from aldehydes and 1,2-allenones catalyzed by N-heterocyclic carbene

Cyclopent-2-enone-4-ols have been prepared highly diastereo-selectively from readily available aromatic aldehydes and 1,2-allenones catalyzed by N-heterocyclic carbene. Mechanistic studies showed that there are four possible pathways.