Rhodium(Ⅲ)-Catalyzed C-H Activation Based On N-nitroso As Ditecting Group

Rh-catalyzed direct C-H functionalization has emerged as a novel strategy in the traditional retro synthetic analysis of total synthesis. It has been a central problem of the methodology during the past decades. This thesis mainly focuses on the reactions of new directing groups in Rh-catalyzed C-H functionalization. The main contents include:The first chapter simply reviews the Rh-catalyzed C-H bond functionalization history and the current status of the field.In chapter2, we report on the development of an N-nitroso directing group method for Rh(Ⅲ)-catalyzed C-H olefination of arenes. The utility of N-nitroso group has enabled the achievement of heightened reactivity, which translates to mild conditions, high yields, and synthetic versatility (broad substrate scope). Comprehensive mechanistic studies (KIE experiment, H-D exchange experiment. reversibility studies, kinetic experiments, competition experiment etc.) support a reaction pathway involving [RhCp*]2+as the catalyst resting state and electrophilic C-H activation as the turnover-limiting step. A catalytically competent five-membered rhodacycle has been structurally characterized, revealing a key intermediate in the catalytic cycle.In chapter3, under the retention of N-nitrosoaniline as substrate, we choose inernal alkyne as the coupling partner and develop a method of Rhodium(Ⅲ)-catalyzed indole synthesis by cross coupling between N-nitrosoanilines and internal alkynes. The reaction can proceed smoothly without external oxidant, which features a distinct internal oxidant, N-N bond, as a reactive handle for catalyst turnover. A diversity of N-nitrosoanilines and alkynes proves to be efficient participants for the transformation.In chapter4, on the base of chapter3, we optimize an acidic condition for the cross coupling between N-nitrosoanilines and inernal alkynes without external oxidant. The versatility of the reaction is exemplified by the tolerance of varied N-alkyl substituents substrate. Further comprehensive mechanistic studies (KIE experiment. H-D exchange experiment, reversibility studies, kinetic experiments, competition experiment etc.) proceed and disclose [RhCp*]2+as generally the catalyst resting state (switchable to [RhCp (OOC’Bu)]+under certain circumstance) and C-H activation as the turnover-limiting step. N2O as a key byproduct is captured by a diversity of detection means (GC, Mass,15N NMR).