Microwave-Assisted Synthesis of Aromatic and Aliphatic Triesters of Resveratrol

Despite intense research on resveratrol, its aromatic esters remain largely unknown. Presented here is a practical, simple, and general protocol for the microwave-assisted preparation of aromatic and aliphatic triesters of resveratrol. Two developed protocols that use conventional and microwave heating, respectively, were compared. Classical reflux led to sluggish esterification, in contrast to microwave-assisted synthesis, which increased the yield and reduced the reaction time from hours to minutes. This microwave protocol was used to synthesize ten aromatic and aliphatic triesters of resveratrol, including resveratryl tricinnamate, tri-3,4-dimethoxycinnamate, tri-2,6-dichlorobenzoate, tri-4-nitrobenzoate, tri-2,3-dimethoxybenzoate, and tri-3,4,5-trimethoxybenzoate, which had not previously been described. Reliable crystallization of all aromatic and some aliphatic triesters was found to be a valuable alternative to time-consuming purification by column chromatography. Crystal structures of resveratryl triisobutyrate and tri-2,6-dichlorobenzoate were determined by X-ray diffraction and were critically compared.