Production of diacetates from propenylphenols: A one-pot two-step approach involving hydroformylation/hydrogenation/O-acylation

A one-pot two-step approach for the synthesis of diacetate esters from propenylphenols was developed. This protocol involves the functionalization of the propenylphenol in two remote sites, performing multiple consecutive and parallel reactions: hydroformylation of the C-C double bond, hydrogenation of the formed aldehyde, and the O-acylation of both phenolic and hydroxy groups of the resulting alcohol. For such a challenging transformation, specific catalytic systems had to be developed, involving Rh complexes and phosphorus(III) ligands for the tandem hydroformylation/hydrogenation, along with 4-dimethylaminopyridine (an organocatalyst) to promote the acylation step by Ac2O. As the presence of Ac2O before the hydrogenation step leaded to undesired side reactions, a one-pot two-step protocol was developed to enhance the selectivity. Eventually, the method allowed to obtain diacetate esters, which are potentially valuable as flavor and fragrance ingredients, from propenylphenols in good to excellent yields (82-96 %).