A simple synthesis of fluoroalkyl substituted dihydrofurans by rhodium(II)-catalyzed 1,3-dipolar reactions

The rhodium(II)-catalyzed reactions of ethyl 2-diazo-fluoroalkylacetoacetate 1 with vinyl ethers have been studied. The reactions of 1a–e with isobutyl vinyl ethers afforded dihydrofuroates 3a–e in good to excellent yields. Further transformation of the dihydrofuroates by acid-catalyzed alcohol elimination could give α-fluoroalkyl-β-furoates readily. Similarly, stable diazo compounds 1a and b reacted with cyclic vinyl ethers to give 1,3-dipolar cycloaddition products. Interestingly, only vinyl C–H insertion compound was obtained concerning the reaction of 1a with 2,5-dimethylfuran. The reaction mechanism was also discussed.