OXIDATIVE DIMERIZATION OF QUINOLINIC NITROXIDES IN THE PRESENCE OF TRICHLORO-ACETIC AND TRIFLUORO-ACETIC ACID - CRYSTAL-STRUCTURES OF -BIS-(1-OXIDE-1,2,6,8A-TETRAHYDROQUINOLINE)YLIDENE AND OF 2,3-DIPHENYLQUINOLINE

Quinolinic nitroxides 1a-c react with trichloro- (TCA) and trifluoro- (TFA) acetic acid to give dimers 3a-c and quinolines 4a-c as the main products. Products 3a-c are explained as arising via the intermediate formation of the radical cation 5, which forms the final dimer through an oxidative dimerization promoted by the TCA or TFA. The formation o f products 4a-c is explained by a Wagner-Meerwein type transposition o f the phenyl group from C-2 to C-3. The disproportionation, which gene rally occurs in the presence of acid for nitroxides having the N-O fun ction conjugated with a pi-system, has been excluded even though quino neimine N-oxides 2a-c were isolated. The structure of compounds 3a and 4a were determined by crystal X-ray analysis.