Transition Metal-Catalyzed Carboamination Of Arylamines With Alkynols And ?-Diazo-?-Ketoesters

Indoles belong to an very important skeleton of many natural products and drug molecules,developing efficient synthetic method for these compounds has always aroused wide interesting in organic synthesis chemistry.In recent years,transition metal catalyzed C-H bond functionalization strategies have provided green access to constructing particular target molecules.On the other hand,transition metal-catalyzed carbamination of olefins,alkynes or others can simultaneously construct C-C and C-N bonds in an one-step chemical transformation.The combination of transition metal-catalyzed C-H bond activation process and the carbamination of unsaturated hydrocarbon molecules will open a novel reaction platform for high atom-and high step-economic synthesis of complex molecules.Based on the above-mentioned review of the transition metal-catalyzed carbamination of unsaturated hydrocarbon molecules,we maded a series of N-aryl-2-pyridinamines molecules which possess heteroatom functional group as functional group,and we further investigated their coupling-reactivities with propargyl alcohol under Rh???-catalytic system.The coupling ring with propargyl alcohol,founding this reaction reaction could assemble 2-acyl3-aryl indole derivatives with good to excellent yields.Meanwhile,different functional group could also tolerate the reaction conditions,the different electron-poor and electron-rich arylamines and acetylene cyclobutanols could be smoothly converted into target compounds.Further mechanism studies showed that this reaction involved the combined Csp²-H bond activation and Csp³-Csp³ bond activation process.The kinetic isotopic experiment demonstrated that the cleavage of the aryl C-H bond is the rate-determinating step for this coupling cyclization.On the basis of Rh???-catalyzed carboamination of N-aryl-2-pyridinamines and propargyl alcohols,we further investigated the carboamination of N-nitrosanilines and?-diazo-?-ketoesters using cheaper cobalt catalysts.The catalytic systeme could quickly afford 2-oxindole compounds library.Control experiments and DFT calculations showed that the reaction was involved in the formation of cobaltacycles,which then reacted with alpha-diazo-beta-ketoesters to form Co???-carbenoid.Then the subsequent Co-mediated Wolff rearrangement produced ketenes,which could be further trapped by cobaltacycles to furnish 2-oxindoles.In order to further extend the reaction scope involving ketenes derived from alpha-diazo-beta-ketoesters,we developed a Zn?OAC?₂-catalyzed the cross-coupling reaction between indoles and lpha-diazo-beta-ketoesters.Gratifyingly,this transformation could smoothly occure to afford 2-acyl indoles in good conversion.This work provided reliable experimental evidence for the Co???-catalyzed carbamination of N-nitrosanilines and ?-diazo-?-ketoesters.