Studies On Transition-metal Catalyzed And Radical Mediated C-H Functionalization

C-H bond is the most common and simple functional group in the organic compound. Direct C-H bond functionalization could obviate tedious, multistep prefunctionality. In addition, it could decrease the formation and emission of wastes due to the high atom economy and thus is environmental friendly. Therefore, the C-H functionalization is of great interest and significance. In this thesis, transition-metal catalyzed directing group-assisted selective C-H bond functionalization into C-C and C-N bonds are studied. Furthermore, heterocyclic compounds are constructed by sequential radical addition and cyclization reactions including the cleavage of C-H bond.The contents in this thesis are summarized as follows:1. A palladium-catalyzed intermolecular C2-acylation of indoles with a-oxocarboxylic acids was developed. The key to this transformation is the installation of a suitable pyrimidyl director that is readily removable on the indole nitrogen atom. The corresponding 2-aroylindoles were obtained in good yields when pyrimidyl was removed. Two strategies were employed in this reaction including decarboxylation and direct C-H bond functionalization.2. A copper-mediated C2-cyanation of indoles using cheap and commercially available acetonitrile as the safe cyanide source was achieved through sequential C-C and C-H bond cleavages. The installation of a removable pyrimidyl group on the indole nitrogen atom is the key for this C2 selectivity. This approach provides a novel and alternative route leading to indole-2-carbonitrile.3. A ruthenium-catalyzed directing group-assisted C7 amidation of indoline C-H bonds with sulfonyl azides was developed. This procedure allows the synthesis of a variety of 7-amino-substituted indolines, which are useful in pharmaceutical. The good functional tolerances, as well as the mild conditions, are prominent feature of this method.4. An iridium-catalyzed phosphoramidation of arene C-H bonds with phosphoryl azide as the amino source was described. The direct C-H phosphoramidation of arenes bearing pyridinyl, pyrazoyl, and quinolinyl as the directing group has good functional group tolerance and occurs smoothly under mild conditions.5. A simple and efficient radical coupling of 2-isocyanobiphenyl with ether to provide 6-alkylated phenanthridine is described. The KIE revealed that the cleavage of sp3 C-H bond would involve in the rate-determining step. In addition, a sequential oxidative radical alkoxycarbonylation and aromatization of 2-isocyanobiphenyl with carbazates was developed to furnish phenanthridine-6-carboxylates. Moreover, a metal-free radical oxidative decarboxylation/cyclization of acylperoxides and 2-isocyanobiphenyls to access 6-arylphenanthridines was also described. Functionalization of sp2 C-H bond and dual C-C bond formation by sequential radical addition and cyclization reactions were involved.6. Radical cyanomethylation/arylation of arylacrylamides to access oxindoles with acetonitrile as the radical precursor was described. This reaction involves dual C-H bond functionalization, including the sp3 C-H of acetonitrile and the sp2 C-H of the phenyl group.