Addition of free radicals to unsaturated systems. Part 23. Photochemical and thermal reactions of trifluoroiodomethane with but-2-ene and but-1-ene

Abstract

Photochemically-initiated addition of trifluoroiodomethane to but-2-ene gives as the major product the 1 : 1 adduct 2-iodo-3-trifluoromethylbutane as a mixture of the erythro- and threo-isomers together with compounds formed via dehydroiodination of the 1 : 1 adduct. Reduction of the 1 : 1 adduct to 2-trifluoromethylbutane is a major process when the reaction tube is shaken. Under thermal conditions fewer products arising via dehydroiodination of the 1 : 1 adduct are detected, but products formed via isomerisation of the reactant olefin to but-1-ene are present in low yield. With but-1-ene initial bidirectional CF₃·radical attack takes place to give the 1 : 1 adducts 1,1,1-trifluoro-3-iodopentane and 1-iodo-2-trifluoromethylbutane in the ratio ca. 19 : 1. Products are also formed via isomerisation of the reactant olefin and via dehydroiodination of the 1 : 1 adducts.