Electron Transfer to Excited Doublet States. Photoirradiation of 10-Methylphenothiazine Cation Radical Perchlorate in Solutions of Phenylacetylene and p-Tolylacetylene in Acetonitrile

Article abstract of DOI:10.1021/jo00300a026

10-Methylphenothiazine cation radical perchlorate (MP.+ClO4-) underwent slow reaction with p-tolylacetylene (PTA) and phenylacetylene (PA) in solution in acetonitrile in the dark.Perchlorate salts (3a and 3b) assumed to be bis-adducts of MP.+ClO4- to the alkyne were formed.In contrast, irradiation of such solutions with visible light (λ > 400 nm) caused oxidation of the alkyne. 2-Methyl-3,6-di-p-tolylpyridine (1a) and 1,4-di-p-tolyl-5,6-dioxa-1,3-cyclohexadiene (2a) were formed from PTA, whereas 2-methyl-3,6-diphenylpyridine (1b) and 1-phenylnaphthalene (4b) were formed from PA.Irradiation of a solution of MP.+ClO4- and 1-pentyne gave only a trace of 2-methyl-3,6-dibutylpyridine (1c).