Study On Rhodium - Catalyzed Indole And Pyrrole C - H Activation / C - C Bond Formation

Indoles and pyrroles are important nitrogen-containing compounds that are commonly occurring structural motifs found in numerous natural products, pharmaceuticals, and biologically active compounds. Therefore, enormous efforts have been devoted to the C-H functionalization of indole and pyrrole scaffold over last several decades. Recently,transition-metal-catalyzed C-H activation has emerged as one of the most powerful tools for functionalization of indoles and pyrroles due to its step- and atom-economical features.These research project of Rhodium catalyzed C-H activation/C-C formation of indole and pyrrole derivatives were discussed in this thesis, and the main contents are as follows:1、Rhodium catalyzed selective C-H activation/arylation of pyrrole derivatives and boric acds had been developed using pyrimidyl group as directing group. Under the optimal conditions, a series of aryl substituted pyrroles could be obtained with high to excellent yields, and the best yield is 95%. A gram-scale experiment for this C–H activation/arylation reaction is successfully carried out with 1.0 mol % loading of catalyst, and the desired product is obtained without significant decrease.2、A simple and versatile method for highly efficient synthesis of various polysubstituted indoles via a sequential one-pot Rh(III)-catalyzed direct C2-H and C7-H alkylation with diazo compounds has been developed. A series of dialkylated indoles were obtained in good to excellent yields under mild reaction conditions. This process features with mild reaction conditions, high efficiency, wide substrate scope and good functional group tolerance. Several control experiments were conducted to demonstrate that the first step of C-H activation occurred at the C2-H bond. According to the experimental results, a plausible mechanism is proposed.3、Base on the work of C2-H and C7-H alkylation of indoles with diazo compounds.The highly efficient and atom-economic Rh(III)-catalyzed direct C-H alkylation of pyrroles bearing electron-deficient system and diazo compounds under mild reaction conditions had been developed. This reaction was considered to proceed most efficiently under the following conditions: 2.0 mol% of Rh as catalyst, 8.0 mol% of AgOAc as additive, as well as a 1:1.2 mol ratio of pyrroles and diazo compounds in MeOH at 30 oC. The attractive features of this protocol include mild conditions, operational simplicity, good functional group tolerance and high efficiency. Particularly, N2 is the sole byproduct in the reaction system.