OMEGA-ALKENYL ALPHA-NITROALKYL RADICALS .3. RADICAL-CHAIN REACTIONS OF OMEGA-ALKENYL ALPHA-HALOGENONITROALKANES

S(RN)1 reactions between 5-bromo-5-nitrohex-1-ene and the nitronate an ions of 2-nitropropane and 5-nitrohex-1-ene failed to give cyclisation of the intermediate alpha-nitroalkyl radical onto the alkene. Reactio n between -endo-5-nitro-exo-6-phenylbicyclo[2.2.1]hept-2-ene 1 and the anion of 2-nitropropane did not undergo an S(RN)1 reaction and Br+ ab straction gave 2-bromo-2-nitropropane and 5-endo-nitro-exo-6-phenylbic yclo[2.2.1]hept-2-ene. BNAH reduction of -endo-5-nitro-exo-6-phenylbic yclo[2.2.1]hept-2-ene 1, 6-bromo-6-nitrohept-1-ene, and 1-bromo-1-nitr o-2-(prop-2-enyl)cyclohexane gave the corresponding nitroalkanes witho ut any cyclisation of the intermediate alpha-nitroalkyl radicals. Init ial results indicate that an iodine atom transfer methodology provides a possible general method for the cyclisation of omega-alkenyl alpha- nitroalkyl radicals. Cyclisation of intermediate alpha-nitroalkyl radi cals, generated by photolysis of clo[2.2.1]hept-5-en-endo-2-yl)-2-iodo -2-nitropropa 5a, gave a good yield of two diastereoisomeric tricyclic iodonitro compounds 6a and 7a. Photolysis of 1-(bicyclo[2.2.1] hept-5 -en-endo-2-yl)-2-iodo-2-nitroethane 5b and 2-(but-3-enyl)-1-iodo-1-nit rocyclohexane 11 also gave the expected products from 5-exo cyclisatio n of the intermediate alpha-nitroalkyl radicals. The tricyclic iodonit ro compound 6a was synthesised from the corresponding endo-methanesulf onate 15, the structure of which was determined by X-ray crystallograp hy.