The Question of Friedel-Crafts Transformylations. Acid-Catalyzed Reactions of Aromatic Aldehydes with Arenes

Article abstract of DOI:10.1021/jo00384a038

The reactions of aromatic aldehydes with various arenes in the presence of Lewis and Broensted acids have been examined with the aim of determining if transformylations occur.No evidence for such transformylations was obtained.The major initial reaction is nucleophilic addition of the arene to the carbonyl group of the aldehyde to produce a diarylmethanol, followed by reaction with a second molecule of arene with elimination of water to produce a triarylmethane.Further reactions include (1) reversible dealkylations/realkylations of triarylmethanes to yield di- and triarylmethanes having aromatic nuclei corresponding to those of both the initial aldehyde and the arene and (2) alkylation, cyclialkylation, and dealkylation reactions that result in the formation of anthracene and/or substituted anthracenes and dihydroanthracenes.The anthracene and dihydroanthracene derivatives are produced in significant amounts only when aluminum chloride is the acid catalyst.The mechanisms of the reactions of aromatic aldehydes with arenes in the presence of aluminum chloride are discussed and compared with reactions of aromatic ketones.