Synthesis of cis-Oriented Vicinal Diphenylethylenes through a Lewis Acid-Promoted Annulation of Oxotriphenylhexanoates

[Image: see text] This study explores the synthesis of cyclic cis-vicinal phenyl ethylenes from oxotriphenylhexanoates. The reaction is a BBr(3)-promoted cyclization of 1,6-ketoesters (1) to five-membered diketo compounds (2). The synthesis is interesting as it constitutes one of the few examples of modular stereoselective synthesis of structures with a cis-oriented vicinal diphenylethylene. The core structure of 2 can be smoothly derivatized, which makes it a promising synthetic building block for further stereoselective synthetic applications.