Rhodium-catalyzed cycloisomerization of allyl propargyl ethers: An efficient synthesis of 3,4-disubstituted furans

Cycloisomerization of allyl propargyl ethers was found to be catalyzed by a cationic rhodium complex to give 3,4-disubstituted furans in one step. Addition of carboxylic acids to the reaction improved the yield of the products. Generation of a rhodium hydride species from a rhodium complex with the carboxylic acids followed by hydrorhodation of the substrate with the rhodium hydride species would be involved in the reaction pathway.