THE REACTIONS OF TRIFLUOROMETHYL AND TRICHLOROMETHYL RADICALS WITH CONJUGATED AND METHYLENE-INTERRUPTED DIENES AND ENYNES

Article abstract of DOI:10.1016/S0022-1139(00)85250-1

The photochemical addition of CF3I to buta-1,3-diene and vinylacetylene in the gas phase gave 1,4-adducts as the main products.In gas phase reactions only products derived from hydrogen abstraction were detected in the CF3I penta-1,3-diene system, but the 1,4-adducts again predominated in the liquid phase.CCl3Br similarly gave a mixture of 1,2- and 1,4-adducts, the latter predominating, on photochemical reaction with penta-1,3-diene.The 1,2-adduct was the main product from the CCl3Br/pent-1-en-4-yn reaction, but some hydrogen abstraction was observed.The preference shown by conjugated dienes to give 1,4-adducts in the trans- configuration is interpreted in terms of steric factors and the propensity of dienes to adopt the s-trans conformation.