New scents using eco-friendly solvents: Oxo synthesis of aldehydes from caryophyllane sesquiterpenes

The rhodium catalyzed hydroformylation (oxo synthesis) of caryophyllene oxide (1) and β-caryophyllene (2), which are among the most abundant sesquiterpenic compounds in nature, leads to aldehydes with pleasant scents. The monoaldehydes derived from 1 and 2 were obtained in high yield under mild reaction conditions. A protocol for the efficient double-hydroformylation of 2 leading to a dialdehyde in a high yield is also described. Furthermore, these reactions can be efficiently carried out in the environmentally benign solvents: dimethylcarbonate, diethylcarbonate, 2-methyl-THF, and p-cymene, to replace conventional toluene and benzene. To the best of our knowledge, this is the first time that these solvents are employed in hydroformylation.