Reactions of 3,4,5-Trimethylbiphenyl and 2,3,4-Trimethylbiphenyl With Nitrogen Dioxide

Reaction of 3,4,5-trimethylbiphenyl (1) with nitrogen dioxide gives four mononitro compounds (3)-(6) and three dinitro compounds (7)-(9). Similar reaction of 2,3,4-trimethylbiphenyl (2) gives three nitroaromatic compounds (11)-(13), three nitrate esters (14)-(16), and two nitro dienones (17) and (18). Dinitro dienone (17) rearranges in solution to give the corresponding hydroxy nitro dienone (19). The differences between the two sets of products are discussed, and an addition-elimination mechanism is proposed for the mode of formation of the nitro dienones (17) and (18). X-Ray crystal structures are reported for compounds (4) and (19).