Oxidative addition reactions of ω-alkenyl nitronate anions

Abstract

Anions are oxidatively added to nitronate anions to yield α-substituted nitroalkanes when potassium hexacyanoferrate(III) is used as oxidant. Oxidation of nitronate anions yields intermediate anitroalkyl radicals, which undergo addition by anions to give intermediate α-substituted nitroalkane radical anions, which are further oxidised to yield the α-substituted nitroalkanes. The nitronate anions used are derived from 5-nitrohex-1-ene, 6-nitrohept-1-ene, endo-5-nitro-exo-6-phenylbicyclo[2.2.1 ]hept-2-ene, and 1-(bicyclo[2.2.1 ]hept-5-en-endo-2-yl)-2-nitropropane. The intermediate α-nitroalkyl radicals underwent addition of anions to form radical anions faster than intramolecular cyclisation onto the ω-alkenes. The α-nitroalkyl radical derived from 1-(bicyclo[2.2.1 ]hept-5-en-endo-2yl)-2-nitropropane underwent cyclisation when the oxidation was carried out in the absence of an added anion. The addition of anions (thiocyanate, benzenesulfinate, 4-chlorobenzenethiolate, and nitrite) to the α-nitroalkyl radicals derived from endo-5-nitro-exo-6-phenylbicyclo[2.2.1]hept-2-ene occurred stereoselectively from the less hindered exo face. Oxidative addition of 4-chlorobenzenethiolate to the nitronate from endo-5-nitro-exo-6-phenylbicyclo[2.2.1]hept-2-ene gave an unusual cyclisation via addition of a thiyl radical to the alkene.