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