Mechanistic Insight into the Rh(III)-Catalyzed C—H Activation of 2-Acetyl-1-Arythydrazines in Water

Abstract

A mechanistic study of the Cp*Rh-catalyzed C-H functionalization of 2-acetyl-1-arythydrazines with diazo compounds in water was carried out by using density functional theory calculations. The results reveal that the acetyl-bonded N-H deprotonation is prior to the phenyl C-H activation. The mechanisms from protonation by acetic acid disagree with the proposal by the Wang group. Different from the Rh(III)-catalyzed C-H activation reported by experimental literature, the rate-determining step of the whole catalytic cycle with an overall barrier of 31.7 kcal mol (IV → TS12-P') is the protonation process of hydroxy O rather than the C-H bond cleavage step. The present theoretical study rationalizes the experimental observation at the molecular level.

Mechanistic insight into ligand‐promoted C–H alkenylation of arenes with alkynes: A computational study

“…The calculation results show that the formation of the complex L1‐I both thermodynamically and kinetically favors the bidentate‐chelation pathway with the exothermicity of −30.2 kcal/mol. Notably, TS1‐2 and TS1’‐2′ are higher than 1 and 2′ in electronic energy, respectively, but the corrected free energies of TS1‐2 and TS1’‐2′ become somewhat lower, indicating the hydroxyl deprotonation of the two pathways(via TS1’‐2′ and TS1‐2 ) without much of a kinetic barrier 33‐35 . In addition, to establish the most stable palladium species, we examined various possible initial Pd II species in the reaction system.…”

“…Notably, TS1-2 and TS1'-2 0 are higher than 1 and 2 0 in electronic energy, respectively, but the corrected free energies of TS1-2 and TS1'-2 0 become somewhat lower, indicating the hydroxyl deprotonation of the two pathways(via TS1'-2 0 and TS1-2) without much of a kinetic barrier. [33][34][35] In addition, to establish the most stable palladium species, we examined various possible initial Pd II species in the reaction system. Some additives, such as Pd(OAc) 2 , 1,4-dichlorobenzene (1a), 4-octane (2a1) and 1,4-dioxane (S) are considered as ligands, which also could coordinate to palladium.…”

Diazo Compounds: Versatile Synthons for the Synthesis of Nitrogen Heterocycles via Transition Metal‐Catalyzed Cascade C–H Activation/Carbene Insertion/Annulation Reactions

“…[10] Interestingly, water was found to be superior to other solvents, while as ilver salt was not necessary in this reaction. [11] They describedt hree different options. Substrates bearing halogen atoms (e.g.,F ,C l, Br) are wellt olerated to give the corresponding products in 73-90% yield.…”

“…Finally, the desired product was formed via tautomerization of intermediate 7 and an intramolecular condensation reaction (Scheme ). However, Wang and co‐workers offered another proposal according to their density functional theroy (DFT) calculations . They described three different options.…”

Computational study on the Rh‐catalyzed chemodivergent oxidative annulation of benzamides and enynes

“…Much efforts have been devoted to their functionalization in the few decades. [1][2][3][4][5][6][7][8][9][10][11] Among them, alkynes are often used as the powerful C2 coupling partners. [12][13][14] Rhodium-catalyzed C H functionalization of arenes has been established as an effective strategy to synthesize desired functional structures.…”