title: Reactivity and mechanistic insight into visible-light-induced aerobic cross-dehydrogenative coupling reaction by organophotocatalysts.
abstract: With visible-light irradiation, a mild, simple, and efficient metal-free photocatalytic system for the facile construction of sp(3)-sp(3) C-C bonds between tertiary amines and activated C-H bonds has been achieved. Spectroscopic study and product analysis demonstrate for the first time that photoinduced electron transfer from N-aryl tetrahydroisoquinolines to eosin Y bis(tetrabutylammonium salt) (TBA-eosin Y) takes place to generate TBA-eosin Y radical anion, which can subsequently react with nucleophiles and molecular oxygen. More strikingly, electron spin resonance (ESR) measurements provide direct evidence for the formation of superoxide radical anions (O(2)(-.)) rather than singlet oxygen ((1)O(2)) during visible-light irradiation. This active species is therefore believed to be responsible for the large rate of acceleration of the aerobic photocatalytic reactions.
authors.affiliation: Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, The Chinese Academy of Sciences, Beijing 100190, PR China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Liu
authors.forename: Ya-Nan
authors.initials: YN
authors.lastname: Li
authors.forename: Hui-Hui
authors.initials: HH
authors.lastname: Zhang
authors.forename: Bin
authors.initials: B
authors.lastname: Chen
authors.forename: Chen-Ho
authors.initials: CH
authors.lastname: Tung
authors.forename: Li-Zhu
authors.initials: LZ
authors.lastname: Wu