Cp~*Co(?)-Catalyzed C-H Amidation Of Olefins

Enamines are usually served as useful precursors for synthesizing nitrogen heterocycles,which extensively exist in biologicals,pharmaceuticals,and natural products.The synthesis of traditional enamines mainly includes the following two methods:(1)the condensation of aldehydes,ketones and amines;(2)the cross-coupling of alkenyl halides with amines.However,these methods have the disadvantages of narrow substrates,harsh reaction conditions,and low selectivity.In recent years,transition metal-catalyzed C-H bond functionalization has attracted wide attention from chemists due to its wide range of substrates and mild reaction conditions,which also is significant in organic synthesis.According to our team's research on transition metal-catalyzed C-H bond activation and related literature investigation,we firstly synthesized the O-(1-phenylvinyl)dimethylcarbamothioate as the substrate.Then,a series of enamine derivatives were synthesized by using[Cp*Co(MeCN)3](SbF6)2 as catalyst,3-phenyl-1,4,2-dioxazol-5-one as aminating reagent and AcOH as additive.Furthermore,all the reactions were performed in mild conditions(rt and air)and a various of enamine derivatives with high yields were obtained.This catalytic system has good Z-selectivity and strong functional group tolerance.In order to explore the applicability of the system,the O-styryl dimethylcarbamothioate was applied to the system,and we found that the amidation product with oxygen and sulfur exchanged was observed under standard conditions.In addition the large-scale reaction was conducted and the yield can reach up to 86%,and the product could be transformed into important heterocyclic molecules 2,5-disubstituted oxazole derivatives in one step,which further demonstrated the application prospect of this reaction in organic synthesis.In the end,the reaction mechanism was explored by H/D exchange experiment,radical trapping experiment,and kinetic isotope effect experiment.A possible reaction mechanism was proposed.