Synthesis and Photo-oxygenation of Some Substituted 1-Benzyl-3,4-dihydroisoquinolines. Mechanism of Enamine Photo-oxygenation

Article abstract of DOI:10.1002/hlca.19820650314

The synthesis of a series of substituted 1-benzyl-3,4-dihydroisoquinolines by Bischler-Napieralski cyclization is described.Competitive methylene blue sensitized photo-oxygenation experiments allowed the determination of relative rates of photo-oxygenation of 1-benzyl-3,4-dihydroisoquinolines.Substituents were shown to affect both the equilibrium concentration of the tautomeric enamine and the overall photo-oxygenation rate.After correcting for differences in enamine concentration, the relative rate data provided a diagnostic probe of the reaction mechanism, which involves transfer of charge in the rate-limiting step.