Title

Visible‐Light‐Mediated [4+2] Annulation of N‐Cyclobutylanilines with Alkynes Catalyzed by Self‐Doped Ti3+@TiO2

Document Type

Article

Publication Date

2017

Keywords

Annulation, Cyclobutylaniline, Photocatalysis, Singlet oxygen, Titanium, Visible light

Abstract

We herein report a visible‐light‐mediated heterogeneous [4+2] annulation of N‐cyclobutylanilines with alkynes catalyzed by self‐doped Ti3+@TiO2. The self‐doped Ti3+@TiO2 is stable under photooxidation conditions, easy to recycle, and can be used multiple times without appreciable loss of activity. Extensive mechanistic studies suggest that the annulation reaction is mediated by singlet oxygen, which is generated through the photosensitization of oxygen in the air by the self‐doped Ti3+@TiO2. In contrast, the homogeneous variant catalyzed by a far more expensive iridium complex proceeds under an inert atmosphere, which indicates a different mechanism. The substrate scopes of the two processes are comparable.

Comments

Principal Investigator: Nan Zheng

Acknowledgements: We thank the University of Arkansas, the Arkansas Bioscience Institute, the National Institute of Health (NIH) (grant number P30 GM103450) from the national Institute of General medical Science, and the NSF Career Award (Award Number CHE‐125539) for generous support of this research. Financial support of the project from the National Science Foundation (CHE‐1213795, P.F.) is also greatly appreciated.

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