General Synthesis of Polyunsaturated Fatty Acid Hydroperoxides Involving a Novel Vinylcyclopropyl Bromide Ring Opening

Article abstract of DOI:10.1021/jo00213a011

A variety of 18- and 20-carbon polyunsaturated fatty acid hydroperoxides were synthesized via an orbital symmetry controlled ring opening of vinylcyclopropyl bromides.Six 20-carbon vinylcyclopropyl bromides (20-25) were synthesized by a route starting from 2-ethoxy-Δ^3,5-dihydropyran (3) and an 18-carbon vinylcyclopropyl bromide by a route starting from propargyl alcohol.All six vinylcyclopropyl bromides underwent facile Ag⁺-asisted ring opening in the presence of excess H2O2 to form the target fatty acid hydroperoxide isomers in good yields.In most cases the products were produced with stereochemical control.The product hydroperoxides formed in this ring-opening reaction are consistent with a mechanism involving the formation of a pentadienyl cation intermediate.A minor product found in the reaction of vinylcyclopropyl bromide 26 provides evidence that homoallylic participation by alkenyl substituents can change the course of the electrocyclic ring opening.