Applied Catalysis A: General, Vol.574, 97-104, 2019
Sustainable route to biomass-based amines: rhodium catalyzed hydroaminomethylation in green solvents
The hydroaminomethylation of bio-renewable alkenes, i.e., estragole, limonene, camphene and beta-pinene, was studied using di-n-butylamine, morpholine, 4-methylpiperidine or 1,2,3,4-tetrahydroisoquinoline as condensation counterparts. This tandem reaction consists of the alkene hydroformylation step followed by the reductive amination of the resulting aldehydes. A series of novel amines with potential bioactivity was obtained in excellent yields. p-Cymene, anisole and ethanol proved to be excellent greener alternatives for toluene, a solvent conventionally used for hydroaminomethylation in most of the previous studies. The performance of p-cymene and anisole was similar to that of toluene; whereas the use of bio-renewable ethanol as a solvent allowed not only to improve the process sustainability but also to obtain much better yields of final amines in several applications, especially, for estragole and beta-pinene, the most challenging substrates in the study.