The photochemistry of 3-nitro-2-cyclohexenone

Article abstract of DOI:10.1016/0040-4039(96)00747-2

3-Nitro-2-cyclohexenone appears to be unreactive when irradiated with ultra-violet light; no rearrangement of the nitro group to a nitrite ester or dimerization of the enone to cyclobutane adducts was observed. Cyclobutane containing photoadducts are also not formed when the electron poor alkenes, acrylonitrile or methyl acrylate are present. However, cyclobutane adducts are produced with more electron rich alkenes. The cycloadducts from reaction with cyclopentene can be reduced with zinc and acid to give a cyclooctanedione identical with the product of de Mayo reaction of cyclohexane-1,3-dione with cyclopentene. Photoadducts are also formed with 2-methylpropene; treatment of these with AIBN followed by hydrogenation yields products identical with those produced by hydrogenation of the photoadducts formed from ultra-violet light irradiation of 2-cyclohexenone with 2-methylpropene. The presence of the nitro group on the cyclohexenone increases the proportion of the head-to-head regioisomers from 13% of the adduct mixture to 63%. Copyright