A Computational Mechanistic Study of Amidation of Quinoline N-Oxide: The Relative Stability of Amido Insertion Intermediates Determines the Regioselectivity

Site-Selective C8-Alkylation of Quinolines with Cyclopropanols: Merging C-H/C-C Bond Activation

The site-selective C8-alkylation of quinolines has been accomplished using cyclopropyl alcohols as the alkylating agents and N-oxide as a weak chelating group in the presence of Co(III) catalysis via merging C-H/C-C bond activation. The use of cyclopropanol as the alkyl source, Co catalysis, substrate scope, HRMS analysis of the reaction intermediate, and late-stage mutation of drug molecules/natural products are the important practical features.

Unravelling nitrene chemistry from acyclic precursors: recent advances and challenges

Recent advances in nitrene chemistry from acyclic precursors are reviewed in this paper.

Metal-Free C-N or C-C Bond Cleavages of α-Azido Ketones: An Oxidative-Amidation Strategy for the Synthesis of α-Ketothioamides and Amides

A novel metal-free oxidative-amidation strategy for the synthesis of α-ketothioamides and amides from α-azido ketones was developed. The C-H bond thionation of α-azido ketones with elemental sulfur could form α-ketothioacyl azide, which was then nucleophilically attacked by amines, causing the cleavage of the C-N bond to afford α-ketothioamides, while amides could be formed with the release of nitrogen gas and cyano anion in the presence of PhI(OAc)₂ by selective C-C bond cleavage.

Ligands and Bases Mediate Switching between Aminocarbonylations and Alkoxycarbonylations in Coupling of Aminophenols with Iodoarenes

The mechanisms of aminocarbonylations and alkoxycarbonylations in coupling of aminophenols with iodoarenes catalyzed by the bidentate phosphorus ligand Pd complexes were explored with theoretical calculations. The origins of chemoselective carbonylation mediated by ligands and bases were disclosed. According to our calculations, the bifurcation points of reaction pathways caused by different ligands and bases combinations are ^L1/L2Int5, a [DPPP/DIBPP]benzoylpalladium(II)iodide complex. The affinity of ^L1/L2Int5 and adducts (K₂CO₃ and DBU), as well as the substrate itself, are the predominant factors of switching from aminocarbonylation to alkoxycarbonylation. The results reveal that K₂CO₃ directly exchanges iodine with ^L1Int5 and assists in hydrogen transfer in the DPPP-K₂CO₃ combination, in which alkoxycarbonylation is more favorable than aminocarbonylation, while for the DIBPP-DBU combination, iodine exchange is achieved by means of the hydrogen bond formed between the carbonyl group on ^L2Int5 and the substrate amino H due to the influence of the ligand, and then iodine exchange occurs; subsequently DBU-assisted amino H transfers to complete the aminocarbonylation. The proton transfer is the step that determines the chemoselectivity in the DPPP-K₂CO₃ combination. The iodine exchange determines the chemoselectivity between aminocarbonylation and alkoxycarbonylation in the DIBPP-DBU one. These results would be helpful to deeply understand the roles of each component in a chemoselective reaction in a multicomponent complex system.

A computational mechanistic study of Ni(0)-catalyzed annulation of aromatic amides with alkynes: the effects of directing groups

The mechanism of Ni(0)-catalyzed annulation of aromatic amides with alkynes was studied theoretically to investigate the effects of directing groups.

Cobalt-catalysed unactivated C(sp3)–H amination: two-state reactivity and multi-reference electronic character

A remarkable two-state reactivity scenario and an unusual multi-reference character have been computationally found in Co-catalysed C(sp³)–H amination. In addition, the investigation on the additive, aminating reagent, metal center, and auxiliary ligand provides implications for development of new catalytic C–H functionalization systems.

Theoretical studies on Rh(iii)-catalyzed regioselective C-H bond cyanation of indole and indoline

Density functional theory calculations were carried out to study the reaction mechanism of the Rh(iii)-catalyzed regioselective C-H cyanation of indole and indoline with N-cyano-N-phenyl-para-methylbenzenesulfonamide (NCTS). This mechanism involves four major steps: C-H activation, cyano group insertion, β-N elimination, and regeneration of active species. How different indole and indoline substrates affect the regioselectivity of C-H bond cyanation has been examined and analyzed in detail. Our calculation results indicate that the regioselectivity of C-H bond cyanation of indole depends on the nucleophilicity of carbon atoms in C-Rh(iii) bonds to the cyano group. For indoline, it can be attributed to the different hybridization platforms of the C-H bond activation.

Delineating Physical Organic Parameters in Site-Selective C-H Functionalization of Indoles

Site-selective C-H functionalization is a great challenge in homogeneous transition-metal catalysis. Herein, we present a physical organic approach to delineate the origin of regioselective amidation of N-acylindoles through Ir(III) catalysis. Bulkiness of N-directing groups of indole substrates and electronics of carboxylate additives were identified as two major factors in controlling C2 and C7 selectivity, and their microscopic mechanisms were studied with DFT-based transition state analysis. Computational insights led us to interrogate a linear free energy relationship, and parametrization of molecular determinants enabled the establishment of an intuitive yet robust statistical model that correlates an extensive number of validation data points in high accuracy. This mechanistic investigation eventually allowed the development of a new C2 amidation and alkenylation protocol of indoles, which affords the exclusive functionalization at the C2 position with up to >70:1 selectivity.

Mechanistic insight into Ni-mediated decarbonylation of unstrained ketones: the origin of decarbonylation catalytic activity

The origin of the Ni-mediated decarbonylation catalytic cycle of unstrained ketones was explored using the DFT calculation method.

Weakly-coordinating N-oxide and carbonyl groups for metal-catalyzed C–H activation: the case of A-ring functionalization

This feature review is focused on recent challenges based on the functionalizations at C-8 and C-5 positions of heterocyclic and quinoidal compounds – a topic that is still rarely explored in the literature.

1,2,3-Triazole-assisted C–H amidation by cobalt(iii) catalysis

This protocol proceeded efficiently under external oxidant-free conditions with the advantages of high atom efficiency and a broad substrate scope.

Mechanism of Nickel-Catalyzed Selective C-N Bond Activation in Suzuki-Miyaura Cross-Coupling of Amides: A Theoretical Investigation

In textbooks, the low reactivity of amides is attributed to the strong resonance stability. However, Garg and co-workers recently reported the Ni-catalyzed activation of robust amide C-N bonds, leading to conversions of amides into esters, ketones, and other amides with high selectivity. Among them, the Ni-catalyzed Suzuki-Miyaura coupling (SMC) of N-benzyl-N-tert-butoxycarbonyl (N-Bn-N-Boc) amides with pinacolatoboronate (PhBpin) was performed in the presence of K₃PO₄ and water. Water significantly enhanced the reaction. With the aid of density functional theory (DFT) calculations, the present study explored the mechanism of the aforementioned SMC reaction as well as analyzed the weakening of amide C-N bond by N-functionalization. The most favorable pathway includes four basic steps: oxidative addition, protonation, transmetalation, and reductive elimination. Comparing the base- and water-free process, the transmetalation step with the help of K₃PO₄ and water is significantly more facile. Water efficiently protonates the basic N(Boc) (Bn) group to form a neutral HN(Boc) (Bn), which is easily removed. The transmetalation step is the rate-determining step with an energy barrier of 25.6 kcal/mol. Further, a DFT prediction was carried out to investigate the full catalytic cycle of a cyclic (amino) (aryl)carbene in the Ni-catalyzed SMC of amides, which provided clues for further design of catalysts.