Hydroformylation and one-pot hydroformylation/epoxy ring cleavage of limonene oxide: a sustainable access to biomass-based multi-functional fragrances

Abstract Naturally occurring, renewable limonene oxide is converted into aldehydes with pleasant scent under oxo (hydroformylation) conditions. Good activity and selectivity are only reached by the careful choice of the catalytic system and the reaction conditions. [Rh(COD)(OMe)]2 was used as the catalyst precursor and PPh3 or (2,4-di-tBuC6H3O)3P as auxiliary ligands, the latter showing better results. The process can be carried in eco-friendly solvents such as anisole, ethanol, dimethylcarbonate (DMC) and diethylcarbonate (DEC). Employing Rh/(2,4-di-tBuC6H3O)3P catalytic system and acetic anhydride or acetic acid as co-reactants, a concomitant one-pot epoxide opening takes place along with hydroformylation, resulting in new acetylated aldehydes potentially useful for the fragrance industry. With the former co-reactant diacetylated products are preferred, while with the latter co-reactant hydroxy acetoxy aldehydes are formed in high yields. The one pot hydroformylation/epoxy ring cleavage process can be also performed in green solvents: DMC, DEC and anisole.