Rhodium carbonyl-catalyzed reactions of internal acetylenes with ethylene and CO in protic solvents, eg, ethanol, gave 3, 4-disubstituted-5-ethyl-2 (5H)-furanones in good yields. By using propylene or methyl acrylate instead of ethylene, small amounts of 5-n-/iso-propyl-2 (5H)-furanones or 5-[2-(methoxycarbonyl) ethyl]-2 (5H)-furanone were obtained.
