Photoaddition of Alkenes to N-Methyl-1,8-naphthalimide in Methanol. Evidence for the Mechanism of the Formation of the Tetracyclic Adducts.

Article abstract of DOI:10.1021/jo00392a021

Irradiation of N-methyl-1,8-naphthalimide (NMN) in the presence of α-methylstyrene (α-MS) or 1,1-diphenylethylene in methanol gives novel tetracyclic imides.The mechanism proposed involves photostimulated electron transfer from the alkene to 1,8-NMN and radical coupling addition of methanol to the resultant radical cation-radical anion pair at the 4-position of the aromatic ring to give an unisolable intermediate with an α,β-unsaturated carbonyl moiety.Absorption of a second photon by this chromophore gives rise to the final product.The predicted regiochemistry and stereochemistry of the reaction were established by using pentadeuterio-α-methylstyrene (16), thus providing strong evidence for the mechanism.