| Abstract
| - The 1,5-diphenyl-1,5-azapentanediyl biradical Ia was generated by photolysis of 1,2-diphenylazacyclopentane (pyrrolidine 1a). Among the reaction pathways followed by Ia, C−N bond reformation withring closure was found to be the predominating process, as determined by separate irradiation of eitherof the pure enantiomers of 1a. Disproportionation was a minor process and took place only via H abstractionby the C5 benzylic radical. Another minor pathway was C5-aryl coupling, with formation of 5-phenyl-2,3,4,5-tetrahydro-1H-benzo[b]azepine (4a), which is equivalent to photo-Claisen rearrangement of 1a.Likewise, the 1,4-diphenyl-1,4-azabutanediyl biradical Ib was generated by photolysis of 1,2-diphenylazacyclobutane (azetidine 1b). This species underwent predominating C2−C3 cleavage, asindicated by the extensive styrene formation. Although N1−C4 bond reformation also took place, this isnot the major pathway occurring from Ib. Besides, C4-aryl coupling to give 4-phenyl-1,2,3,4-tetrahydroquinoline (4b) was also observed. All the possible reaction pathways were theoretically studiedat the UB3LYP/6-31G* computational level; the results were found to be in good agreement with theexperimental observations.
|
