Rhodium-Carbene Mediated Heterocyclic Synthesis And Palladium-Carbene Catalyzed Bio-orthogonal Reaction

Metal stabilized carbene has been widely applied in organic chemistry. For instance, the cyclopropanation reactions and the C-H/X-H insertion reactions are powerful tools for synthesis. On the other hand, N-heterocyclic Carbene (NHC), as an important class of carbene, is indispensible for catalytic reactions. The study of carbene is now focusing on developing efficient catalysts and exploiting new carbene resources.In this paper, we will introduce our work in application of N-sulfonyl-1,2,3-triazoles for hetero-cyclic compounds synthesis, and in the developing of new ligands for metal catalyzed bio-orthogonal reaction. This paper can be divided into three parts as follows:1. Rhodium-catalyzed C-H insertion of N-sulfonyl-1,2,3-triazoles is presented, and3-methylene-2,3-Dihydrobenzofurans are synthesized. Further treatment of the products with palladium catalyst would give2,3-disubstitutedbenzofurans.2. Rhodium-catalyzed trans-annulation of N-sulfonyl-1,2,3-triazoles and ring opening reactions of epoxides is developed. A number of single regio-selective product3,4-dihydro-2H-1,4-oxazines is obtained in moderate yields.3. We synthesized some N-heterocyclic carbene (NHC)-stabilized palladium complexes for cross-couplings of biomolecules under mild conditions in water. Pd-NHC complexes were demonstrated to be efficient catalysts for the Suzuki-Miyaura coupling of various unnatural amino acids and proteins. We further utilized this catalytic system for the rapid bio-orthogonal labeling of proteins on the surfaces of mammalian cells.