Guerbet Alcohols: From Processes under Harsh Conditions to Synthesis at Room Temperature under Ambient Pressure

Abstract

AbstractA novel synthetic approach towards Guerbet alcohols, which are important intermediates in the production of plasticizers, lubricants, and surfactants, was developed. In contrast to the harsh reaction conditions of Guerbet alcohols produced today, which include high temperatures, the new developed process runs at room temperature. The key feature of this alternative process is the combination of organocatalytic and enzymatic steps towards a chemoenzymatic synthesis. In detail, the piperidinyloxyl‐catalyzed oxidation of 1‐hexanol by using hypochlorite and the lysine‐catalyzed homoaldol condensation of the resulting aldehyde were combined with two subsequent enzymatic reductions of the C=C and C=O bonds of the in situ formed 2‐branched α,β‐unsaturated aldehyde by means of an ene reductase from Gluconobacter oxydans and an alcohol dehydrogenase from Rhodococcus sp. under in situ cofactor regeneration. The desired 2‐branched aliphatic primary alcohol was obtained with high conversion and selectivity and without the need for intermediate purifications.