The photoinduced ring-opening reaction of 1-(2-naphthoyl)aziridine in alcohols

Photoreactions of 1-(2-naphthoyl)aziridine (1) in a series of alcohols have been studied at λex. 313 nm and room temperature under deaerated conditions. Irradiation of (1) in methanol gave N-(2-methoxyethyl)naphthalene-2-carboxamide (2a) selectively, while N-ethylnaphthalene-2-carboxamide (3) was produced in ethanol and propan-2-ol. The competitive formation of N-(2-t-butoxyethyl)-naphthalene-2-carboxamide (2b) and (3) occurred in t-butyl alcohol. These alcohols formed 1:1 hydrogen bonds with (1) in their ground states. The quantum yield for the fluorescence emission (ΦF) of (1) increased and the red shift of the emission maximum was enhanced with the increase in hydrogen bonding ability of the alcohols. Penta-1,3-diene quenched the formation of (3) but not (2a) or (2b). The Stern–Volmer plot for quenching of the formation of (3) by penta-1,3-diene was linear in propan-2-ol, whereas it curved downward to approach a definite value in ethanol or t-butyl alcohol. The quantum yield of (2b) in t-butyl alcohol-containing mixed solvents tended to increase with the increased dielectric constant (Iµ).