金属有机化学ppt.pptx
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1、Research background2The significance of C(sp3)-H activation leading to C-N bond formation has been extensively exemplified because C-N linkages are ubiquitous in pharmaceuticals, biologically active compounds, and natural products.Consequently, the direct amination/amidation of unactivated C(sp3)-H
2、bonds has received increasing attention.In the past decade, only limited examples of direct amination of C(sp3)-H Bonds has been reported by using palladium, rhodium(II),copper, iridium,and other catalysts.Recently, rhodium(III)-catalyzed C-H activation has been increasingly explored, and provides u
3、nique synthetic methodologies with high activity,selectivity, broad substrate scope, and functional-group tolerance.Despite these attractive processes, the coupling reactions are mostly based on C(sp2)-H activation.3Research backgroundThus,there are only a few examples on the functionalization of un
4、activated C(sp3)-H bonds using rhodium(III) catalysis, as in the coupling with alkynes, activated forms of arenes,and azides.Recently, Chang and co-workers reported an elegant iridium(III)-catalyzed amidation for a broad scope of C(sp3)-H bonds using organic azides.Despite the progress, rhodium(III)
5、-catalyzed C(sp3)-H activation reactions, especially amidation reactions, typically suffer from limited substrate scope and harsh reaction conditions, and only amidation of benzylic C-H bonds, such as that in 8-methylquinolines, has been realized.4The challenges associated with C(sp3)-H bond activat
6、ion can be ascribed to the steric hindrance of C(sp3)-H bonds and the low reactivity of the resulting Rh-C(alkyl) species.Therefore, the stability, coordinating capacity, and reactivity of the coupling partner are major criteria for our design.Research background5We now report a mild rhodium(III)-ca
7、talyzed C(sp3)-H amidation for a broad scope of substrates, including 8-alkylquinoline and aliphatic cyclic and acyclic ketoximes.This amidation reaction utilizes 3-substituted 1,4,2-dioxazol-5-ones as theamide sources, and they are particularly attractive nitrenetransfer reagents owing to their hig
8、h activity, stability, and synthetic accessibility.6We initiated our studies with the screening of reaction conditions in the coupling of 8-methylquinoline (1a) with 3-phenyl-1,4,2-dioxazol-5-one (2a; Table 1).a Reactions were carried out by using RhCp*Cl22 (4.0 mol%)/AgSbF6 (16 mol%), AgOAc (8 mol%
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