Phototransposition reactions of methyl-substituted benzotrifluorides: proof of the role of trifluoromethyl-substituted carbon

Irradiation in acetonitrile of any one of the six isomers of dimethylbenzotrifluoride 8 resulted in efficient photoisomerization to the others. The dominant processes in these phototransposition reactions divides the isomers into two triads. The first consists of 8-2,6 (2,6-dimethylbenzotrifluoride), 8-2,3, and 8-3,4; the second consists of 8-3,5, 8-2,4, and 8-2,5. Moreover, irradiation of 2,6-dideuterio-4-methylbenzotrifluoride 5-d(2) resulted in formation of 5,6-dideuterio-3-methylbenzotrifluoride 6-d(2). These observations demonstrate that it is the trifluoromethyl-substituted carbon that is the migratory one in these reactions.