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

Abstract

Photoreactions of 1-(2-naphthoyl)aziridine (1) in a series of alcohols have been studied at λ_ex. 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 (Φ_F) 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 (ε).