Synthesis of Dihydropyrans and Dihydrofurans via Radical Cyclization of Unsaturated Alcohols and 1,3‐Dicarbonyl Compounds

Abstract

AbstractThe oxidative cyclization reactions of 1,3‐dicarbonyl compounds 1a–1c and α,β‐unsaturated alcohols 2a–2f with Mn(OAc)3 were performed, leading to dihydrofurans. Treatment of 1a and 1b with 2‐methylbut‐3‐en‐2‐ol (2a) gave dihydrofurans 3aa and 3ba, and dihydropyrans 4aa and 4ba, as unexpected products. While the reaction of 2‐methylbut‐3‐yn‐2‐ol (2b) with acetylacetone (1b) yielded a bifuran, ethyl acetoacetate (1a) led to a mixture of furan, bifuran, and salicylate derivatives. Besides, surprisingly, styryl‐substituted dihydrofurans were obtained from the reactions of 1,3‐dicarbonyl compounds and (3E)‐2,4‐diphenylbut‐3‐en‐2‐ol. The reaction mechanisms were proposed for the formation of the different products, considering intermediates in these reaction mixtures.