A First Example of Cobalt-Catalyzed Remote C-H Functionalization of 8-Aminoquinolines Operating through a Single Electron Transfer Mechanism

Abstract

The development of new CH functionalization protocols based on inexpensive cobalt catalysts is currently attracting significant interest. Functionalized 8-aminoquinoline compounds are high-potential building blocks in organic chemistry and pharmaceutical compounds and new facile routes for their preparation would be highly valuable. Recently, copper has been applied as catalyst for the functionalization of 8-aminoquinoline compounds and found to operate through a single electron transfer (SET) mechanism, although requiring elevated reaction temperatures. Herein, we described the first example of a cobalt-catalyzed remote CH functionalization of 8-aminoquinoline compounds operating through a SET mechanism, exemplified using a practical and mild nitration protocol. The reaction uses inexpensive cobalt nitrate hexahydrate [Co(NO3)2⋅6 H2O] as catalyst and tert-butyl nitrite (TBN) as nitro source. This methodology offers the basis for the facile preparation of many new functionalized 8-aminoquinoline derivatives

We acknowledge financial support from the ERC for the Starting Grant Project ERC-2011-StG-277801 to X.R and MINECO of Spain for CTQ2013-43012-P to X.R. and A.C., and a RyC contract to A.C. We thank the MECD for a FPU PhD grant to O.P and Generalitat de Catalunya (2014 SGR 862). X.R. also thanks ICREA for ICREA-AcadÀmia 2010 and 2015 awards. We are also grateful to X. Fontrodona (Xray crystallography), Dr. L. Gýmez (HR-MS) and STRUdG