Formal hydride transfer mechanism for photoreduction of 3-phenylquinoxalin-2-ones by amines. Association of 3-phenylquinoxalin-2-one with aliphatic amines

De la Fuente, JR; Cañete Á.; Zanocco, AL; Saitz C.; Jullian C.

Abstract

The photophysical and photochemical behavior of 1-methyl-3-phenylquinoxalin-2-one (MeNQ) and 3-phenylquinoxalin-2-one (HNQ) in the presence of amines is reported. While HNQ fluorescence shows an auxochromic effect and a bathochromic shift with added amines, explained by association of HNQ with amine in the ground state and emission from both excited species HNQ* and [HNQ-amine]*, both MeNQ and HNQ are photoreduced efficiently on irradiation in the presence of amines, leading to the semireduced quinoxalin-2-ones, MeNQH(-) and HNQH(-), respectively, via an electron-proton-electron transfer, with unit quantum yields at high amine concentrations. The semireduced quinoxalin-2-ones XNQH(-) (X = H, Me) revert almost quantitatively to the parent XNQ in a dark thermal reaction with an activation free energy for MeNQH(-) of 17.4 and 25.9 kcal/mol in acetonitrile and benzene, respectively. Kinetic and spectroscopic (UV and NMR) evidence supports the proposed reaction mechanism for the reversible photoreduction.

Más información

Título según WOS: Formal hydride transfer mechanism for photoreduction of 3-phenylquinoxalin-2-ones by amines. Association of 3-phenylquinoxalin-2-one with aliphatic amines
Título de la Revista: Journal of Organic Chemistry
Volumen: 65
Número: 23
Editorial: American Chemical Society
Fecha de publicación: 2000
Página de inicio: 7949
Página final: 7958
Idioma: English
URL: http://pubs.acs.org/doi/abs/10.1021/jo000992r
DOI:

10.1021/jo000992r

Notas: ISI