Rhodium-Catalyzed Carbonylative Addition-Cyclization Approach to Furans

Significance

While attempting the rhodium-catalyzed synthesis of γ-hydroxy ketones by reaction of propargylic alcohols with arylboronic acids, Sauthier, Castanet and co-workers stumbled on an unexpected formation of a furan derivative, formed by dehydrative cyclization of the in situ formed hydroxy enone. An extensive screening ­involving the solvent, temperature, and rhodium source afforded the optimal conditions as shown in the scheme. The addition of 2.5 mol% LiI led to ˜50% increase in the yield. The role of LiI was not speculated. The yields range from moderate to good, except when the aryl ring contains meta or ortho substituents (<10% yield). The substrate scope was insufficiently studied; most notably heteroaromatic boronic acids were not investi­gated.