Herein, we report an efficient and practical strategy for the synthesis of five types of imidazo[2,1-a]isoquinolines via Cp*RhIII-catalyzed [4+2] annulation of 2-arylimidazoles and α-diazoketoesters, whose structural and substituted diversity at 5- or 6-position can be precisely controlled by the α-diazoketoester coupling partners. Compared with previous reports, in this study, we merged two attractive C-C cleavage strategies (retro-Claisen and decarboxylation) into the classical C-H functionalization/condensation process by choosing appropriate ester groups (-COOEt, -COOtBu or -COOiPr) or inexpensive additives (HOAc or KOAc). Moreover, the synthetic efficacies of these methods were demonstrated by the concise synthesis of several bioactive compounds and the late-stage modification of representative drugs.

A highly efficient synthesis of 3-formyl imidazo[1,2-a]pyridine and imidazo[1,2-a]pyrimidine, under Cu-catalyzed aerobic oxidative conditions and by utilizing ethyl tertiary amines as carbon sources, is disclosed. A novel activation mode of ethyl tertiary amines in which simultaneous selective cleavage of C-C bond and C-N bond of ethyl group with molecular oxygen as terminal oxidant in this one-pot protocol is reported for the first time. This reaction features broad substrate scope, good functional group tolerance, as well as diversified and valuable products.

An unprecedented substituent-controlled chemoselective cleavage of C═C double bond or C(sp(2))-C(CO) bond along with aerobic phosphorylation of α,β-unsaturated carbonyl compounds with H-phosphonates through a radical process has been disclosed. The current strategy provides an access to β-ketophosphonates under mild conditions with a wide substrate scope.

An efficient one-pot cascade process via unprecedented quadruple cleavage of BrCFCOOEt with primary amines to afford valuable fluorine-containing heterocycles is described, in which BrCFCOOEt plays a dual role as a C1 synthon and a difluoroalkylating reagent for the first time. Mechanistic studies supported by DFT calculations suggest that a base plays an active role in the formation of the key intermediate isocyanides generated in situ from primary amines and difluorocarbene.