Electronic and steric factors for enhanced selective synthesis of 2-ethyl-1-hexanol in the Ir-complex-catalyzed Guerbet reaction of 1-butanol

1-Butanol is a potential bio-based fermentation product obtained from cellulosic biomass. As value-added chemical, 2-ethyl-1-hexanol (2-EH) can be produced by Guerbet conversion 1-butanol. This work reports the enhanced catalytic reaction of 1-butanol to 2-EH series Cp*Ir complexes (Cp*: 1,2,3,4,5-pentamethylcyclopenta-1,3-diene) coordinated bipyridine-type ligands bearing an ortho-hydroxypyridine group with electron-donating and Cl− anion. The activity complex increased increasing electron density bipyridine ligand when functionalized para-NMe2 groups. A record turnover number 14047 was attained. mechanistic study indicated that steric effect ethyl on α-C 2-ethylhexanal (2-EHA) conjugation C=C–C=O in 2-ethylhex-2-enal (2-EEA) benefits high selectivity inhibiting cross-aldol 2-EHA 2-EEA butyraldehyde. Nuclear magnetic resonance revealed formation carbonyl via KOH.