Replacing syngas by formic acid and acetic anhydride with advantages: tandem carbonylation of renewable terpenes and propenylbenzenes

The introduction of aldehyde and acetate functionalities in renewable terpenes and propenylbezenes provides useful feedstocks for fine chemicals, especially in the flavor and fragrance segment. Herein we report the rhodium catalyzed hydroformylation and the tandem hydroformylation/hydrogenation/O-acylation of biomass based propenylbenzenes and terpenes with a mixture of formic acid (FA) and acetic anhydride (Ac2O) as a cheaper and less dangerous alternative for flammable and toxic syngas (carbon monoxide and hydrogen mixture) used in the conventional hydroformylation. In addition, we were able to perform the consecutive aldehyde hydrogenation, followed by O-acetylation, formally adding a methyl acetate molecule in a C-C double bond in a tandem process, which was not feasible with the conventional hydroformylation. For propenylbenzenes containing a phenol moiety, the parallel acetoxylation of this group also took place. The protocol allowed to obtain aldehydes and mono- or diacetate esters, which are potentially valuable as fragrance components.