Hydrogen Transfer Reduction of Aldehydes with Alkali-Metal Carbonates and Iridium NHC Complexes

Some neopentyl-substituted NHC iridium complexes catalyze the reduction of a variety of aldehydes and even enolizable aldehydes by hydrogen transfer from refluxing 2-propanol with alkali-metal carbonate bases. Imidazole and 1,2,4-triazole complexes had comparable activities. The aldehydes could also be reduced more slowly using a mild carbonate base and no iridium complex.