Fully Substituted Furans by One-Pot Propargylation-Cycloisomerization

Significance

A ruthenium-catalyzed, TFA-mediated reaction of propargylic alcohols with 1,3-dicarbonyl compounds leads to the formation of tetra­substituted furans in modest to excellent yields. The reaction proceeds via initial condensation to form a γ-keto alkyne followed by Ru-catalyzed cycloisomerization. The reaction with tert-butyl acetoacetate as the β-diketo component gave a trisubstituted furan, a result of TFA-induced hydrolysis and decarboxylation. A propargylated intermediate was isolated, characterized, and shown to undergo cyclization to a furan product. Significant R¹ substitution patterns were not widely explored; however, one internal propargylic alcohol (phenylbut-2-yn-1-ol) was successfully converted into a furan thus indicating potential for 5-Me variation.