Nickel And Cobalt-catalyzed C-H Functionalization Based On Directing Strategy

Nowadays transition-metal-catalyzed direct functionalization of C-H bond has attracted more and more interest as high atom,step economic and no pre-functionalized substrates need.The developed method always employs directing strategy and precious second-and third-row transition metals to achieve specified C-H bond activation functionalization.However,due to earth-abundant,inexpensive and environmentally friendly of first-row transition metals,their study has received tremendous attention and becomes a hot point in organic chemistry recently.At the same time the first-.row transition metals will perform differently from corresponding noble ones,so it is meaningful to study their catalytic property individually.We think it will enrich the diversity and application scope of C-H activation in the organic reactions.Base on this,using directing strategy,this dissertation is mainly focus on base metal nickel and cobalt-catalyzed C-H activation to construct C-S and C-C bond,which includes:1.Nickel-catalyzed thiolation of unreactive C(sp2)-H and C(sp3)-HWe have developed a strong catalytic system involving nickel and BINOL,this system can affect unreactive C(sp2)-H and C(sp3)-H direct thiolation using various disulfides as the sulfur source.The protocol features a broad substrate scope,high functional group tolerance,and good compatibility with heterocycle substrates providing an efficient synthetic pathway to access diverse disulfides.2.Nickel-catalyzed direct C-H trifluoroethylation of heteroarenesA highly selective nickel-catalyzed C-H trifluoroethylation of heteroarenes including indole,pyrroles,furans,and thiophenes was developed with the assistance of a monodentate directing strategy.This protocol tolerates various functional group,and use commercially available CF3CH2I as an alkylation reagent.The synthetic and medical post modification potential of this protocol was demonstrated by gram scale synthesis and easy removal of the pyridine directing group.Preliminary studies suggested that this reaction might proceed through radical mechanism.3.Cobalt-Catalyzed Alkylation of Primary C(sp3)-H Bonds with Diazo compoundsCobalt(III)-catalyzed alkylation of 8-methylquinolines with diazo compounds through primary C(sp3)-H cobaltation/carbenoid insertion has been realized.The reaction is highly efficient,scalable and tolerates a variety of functional groups.Furthermore,the unique protocol can be applied to the synthesis of azatricyclic antibiotic compounds.Mechanism study demonstrated that it may proceed through quinolyl-directeU C(sp3)-H cobaltation,Co carbene formation,migratory insertion and subsequent protonation to complete the catalytic cycle.