Regiocontrolled Formation of 4,5-Dihydro-3(2H)-furanones from 2-Butyne-1,4-diol Derivatives. Synthesis of Bullatenone and Geiparvarin

Two new methods for selective hydration of 1,1,4-trisubstituted 2-butyne-1,4-diols (1) to give 4,5-dihydro-3(2H)-furanone derivatives are reported. The first involves selective monoacetylation of the less hindered hydroxyl group of 1followed by Ag(I)-catalyzed rearrangement and cyclization to give 3-acetoxy-2,2,5-trisubstituted 2,5-dihydrofurans (2). Final hydrolysis yielded 2,2,5-trisubstituted 4,5-dihydro-3(2H)-furanones. Oxidation of the enol acetates 2with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone gave 3(2H)-furanones. The new method was applied to the synthesis of naturally occurring 3(2H)-furanones such as bullatenone and geiparvarin from the corresponding 2-butyne-1,4-diol derivatives. The second approach is concerned with the synthesis of the opposite regioisomer, 2,5,5-trisubstituted 4,5-dihydro-3(2H)-furanones, from diols 1with a polymer reagent Hg/Nafion-H.