Cobalt(Ⅱ)-Catalyzed Decarboxylative C-H Activation/Annulation Cascades: Regioselective Access To Isoquinolones And Isoindolinones

Transition-metal-catalyzed C-H functionalization has proven to be an effective strategy for the construction of various organic frameworks.Isoquinolones and isoindolinones have been widely investigated as important structural motifs in a variety of natural drugs and pharmaceuticals.Unfortunately,the preparation of isoquinolones and isoindolinones often requires different starting materials and synthetic routes,which is cost-ineffective.Thus,it is highly desirable to develop an innovative methodology to obtain these heteroarenes from common starting materials in a controllable way.A new cobalt(Ⅱ)-catalyzed decarboxylative C-H activation/annulation of benzamides and alkynyl carboxylic acids has been described.Alkynyl carboxylic acids were firstly employed as the coupling partners using inexpensive Co(OAc)2·4H2O as the catalyst.This method enables a switchable cyclization to isoquinolones and isoindolinones with excellent selectivity.In the TFE,catalytic amount of Ag2 O was adopted as co-catalyst and O2(from air)as a terminal oxidant for the preparation of isoquinolones.In the DMF,stoichiometric Ag2 O was employed as an oxidant for the preparation of isoindolinones.Moreover,on the basis of a series of control experiments,a plausible mechanism for the catalytic systems was proposed.