Open-Shell Phenalenyl in Transition Metal-Free Catalytic C–H Functionalization

• Published in: Journal of organic chemistry 2016-03, Vol.81 (6), p.2432-2441
• Main Authors: Paira, Rupankar, Singh, Bhagat, Hota, Pradip Kumar, Ahmed, Jasimuddin, Sau, Samaresh Chandra, Johnpeter, Justin P, Mandal, Swadhin K
• Format: Article
• Language: English
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/acs.joc.6b00002

Open-shell phenalenyl chemistry has widely been explored in the last five decades demonstrating its potential in various applications including molecular switch, spin memory device, molecular battery, cathode material, etc. In this article, we have explored another new direction of open-shell phenalenyl chemistry toward transition metal-free catalytic C–H functionalization process. A phenalenyl ligand, namely, 9-methylamino-phenalen-1-one (4a), promoted chelation-assisted single electron transfer (SET) process, which facilitates the C–H functionalization of unactivated arenes to form the biaryl products. The present methodology offers a diverse substrate scope, which can be operated without employing any dry or inert conditions and under truly transition metal based catalyst like loading yet avoiding any expensive or toxic transition metal. This not only is the first report on the application of phenalenyl chemistry in C–H functionalization process but also provides a low-catalyst loading organocatalytic system (up to 0.5 mol % catalyst loading) as compared to the existing ones (mostly 20–40 mol %), which has taken advantage of long known phenalenyl based radical stability through the presence of its low-lying nonbonding molecular orbital.