Mechanism for the Carboxylative Coupling Reaction of a Terminal Alkyne, CO2, and an Allylic Chloride Catalyzed by the Cu(I) Complex: A DFT Study

Origins of regio- and stereoselectivity in Cu-catalyzed alkyne difunctionalization with CO2 and organoboranes

The anti-to-Cu 1,2-migration of alkynyl boronates is critical for the 1,1-E-selective difunctionalization of terminal alkynes with CO2 and organoboranes.

Computational determination of the mechanism of the Pd-catalyzed formation of isatoic anhydrides from o-haloanilines, CO, and CO2

The palladium-catalyzed annulation of o-haloanilines with carbon monoxide (CO) and carbon dioxide (CO₂), discovered by Wen-Zhen Zhang and co-workers, provides a convenient method to synthesize isatoic anhydrides. We explored the mechanism of this reaction, particularly the order of the reaction of CO and CO₂ and the effect of the base, using density functional theory (DFT) calculations (ωB97X-D and M06). It was found that the base-assisted N-H bond activation through a concerted metalation-deprotonation (CMD) mechanism is a requisite for carboxylation, and the carboxylation proceeds via the nucleophilic attack of the (Pd)NH nitrogen on CO₂. The results show that carbonylation occurs prior to carboxylation, because the facile and exergonic carbonylation greatly decreases the energies of the following intermediates and transition states. The mechanistic exploration of the alternative pathways (e.g., mono-carbonylation and carboxylation) and the comparison with the annulation mechanism of the o-iodobenzylamine substrate further demonstrate the perfect cooperation of CO and CO₂ in constructing an anhydride moiety for o-haloanilines.

Is Cu(iii) a necessary intermediate in Cu-mediated coupling reactions? A mechanistic point of view

The different pathways have been summarized to disclose the key intermediate in copper-mediated coupling reactions.

C-H Bond Carboxylation with Carbon Dioxide

Carbon dioxide is a nontoxic, renewable, and abundant C₁ source, whereas C-H bond functionalization represents one of the most important approaches to the construction of carbon-carbon bonds and carbon-heteroatom bonds in an atom- and step-economical manner. Combining the chemical transformation of CO₂ with C-H bond functionalization is of great importance in the synthesis of carboxylic acids and their derivatives. The contents of this Review are organized according to the type of C-H bond involved in carboxylation. The primary types of C-H bonds are as follows: C(sp)-H bonds of terminal alkynes, C(sp² )-H bonds of (hetero)arenes, vinylic C(sp² )-H bonds, the ipso-C(sp² )-H bonds of the diazo group, aldehyde C(sp² )-H bonds, α-C(sp³ )-H bonds of the carbonyl group, γ-C(sp³ )-H bonds of the carbonyl group, C(sp³ )-H bonds adjacent to nitrogen atoms, C(sp³ )-H bonds of o-alkyl phenyl ketones, allylic C(sp³ )-H bonds, C(sp³ )-H bonds of methane, and C(sp³ )-H bonds of halogenated aliphatic hydrocarbons. In addition, multicomponent reactions, tandem reactions, and key theoretical studies related to the carboxylation of C-H bonds are briefly summarized. Transition-metal-free, organocatalytic, electrochemical, and light-driven methods are highlighted.

Mechanistic insight into the silver-catalyzed cycloaddition synthesis of 1,4-disubstituted-1,2,3-triazoles: the key role of silver

By using DFT calculations, we disclose the reason why silver(i) catalytically promotes the activity and regioselectivity of the cycloaddition of 1,4-disubstituted-1,2,3-triazoles.

Mechanisms of CO2 Incorporation into Propargylic Amine Catalyzed by Ag(I)/Amine Catalysts

Density functional theory calculations are carried out to explore the detail mechanisms of CO₂ incorporation into propargylic amine catalyzed by Ag(I)/amine catalysts. Our calculations reveal that the whole reaction involves Lewis acid catalysis and Lewis base catalysis stages, and the outcomes of this reaction critically depend on the basicity of amine. A weaker base (i.e., DABCO) makes the Ag center more acidic, thus favoring the Lewis acid catalysis, resulting in benzoxazin-2-one. However, the following rearrangement of benzoxazin-2-one requires a stronger base (i.e., DBU) to stabilize its deprotonated form. Thus, the product selectivity could be subtly tuned by the choice of amine and the condition control, consistent with the experimental observations.

Mechanistic Insights into the Ni-Catalyzed Reductive Carboxylation of C-O Bonds in Aromatic Esters with CO2 : Understanding Remarkable Ligand and Traceless-Directing-Group Effects

The mechanism of the Ni⁰ -catalyzed reductive carboxylation reaction of C(sp² )-O and C(sp³ )-O bonds in aromatic esters with CO₂ to access valuable carboxylic acids was comprehensively studied by using DFT calculations. Computational results revealed that this transformation was composed of several key steps: C-O bond cleavage, reductive elimination, and/or CO₂ insertion. Of these steps, C-O bond cleavage was found to be rate-determining, and it occurred through either oxidative addition to form a Ni^II intermediate, or a radical pathway that involved a bimetallic species to generate two Ni^I species through homolytic dissociation of the C-O bond. DFT calculations revealed that the oxidative addition step was preferred in the reductive carboxylation reactions of C(sp² )-O and C(sp³ )-O bonds in substrates with extended π systems. In contrast, oxidative addition was highly disfavored when traceless directing groups were involved in the reductive coupling of substrates without extended π systems. In such cases, the presence of traceless directing groups allowed for docking of a second Ni⁰ catalyst, and the reactions proceed through a bimetallic radical pathway, rather than through concerted oxidative addition, to afford two Ni^I species both kinetically and thermodynamically. These theoretical mechanistic insights into the reductive carboxylation reactions of C-O bonds were also employed to investigate several experimentally observed phenomena, including ligand-dependent reactivity and site-selectivity.

Theoretical studies on CuCl-catalyzed C-H activation/C-O coupling reactions: oxidant and catalyst effects

Copper-complex catalyzed coupling reactions have been widely applied in the production of many important organic moieties from a synthetic perspective. In this work, a series of density functional theory (DFT) calculations, employing the B3LYP + IDSCRF/DZVP method, have been performed for a typical CuCl-catalyzed C-O cross-coupling reaction. The novel reaction mechanism was reported as four successive processes: oxidative radical generation (ORG) or oxidative addition (OA), hydrogen abstraction (HA), C-H activation/reductive elimination, and separation of product and recycling of catalyst (SP & RC). Our calculations provided a deep understanding on the dissimilar chemical activities associated with varying the oxidants used; detailed energy profile analyses suggested that the first oxidation process could proceed via either of the two competing channels (ORG and OA mechanisms) which is the basis to explain the different experimental yields. In addition, our molecular modelling gave theoretical evidence that Cu(ii) → Cu(i) reduction by solvent DMF (and a water molecule) might serve as a preliminary step to produce some more active Cu(i) species that could subsequently be oxidized into Cu(iii) favorably. In contrast, the Cu(ii) → Cu(iii) direct pathway was estimated to be prohibited from thermodynamics. All the calculation results in this work are parallel with the experimental observations.

Using a traceless directing group for the silver-mediated synthesis of 3-trifluoromethylpyrazoles: a computational study on the mechanism and origins of regioselectivity

The silver-mediated one-pot synthesis of 3-trifluoromethylpyrazoles using a traceless directing group was investigated by density functional theory (DFT) calculations.

How the Coordinated Structures of Ag(I) Catalysts Affect the Outcomes of Carbon Dioxide Incorporation into Propargylic Amine: A DFT Study

Density functional theory calculations have been carried out to explore the detailed mechanisms for carbon dioxide incorporation of N-unsubstituted propargylic amine catalyzed by Ag(I) catalysts. We show that the reaction undergoes substrate adsorption or displacement, isomerization from amine-coordinated species to the alkyne-coordinated species, CO₂ attack, and proton transfer, giving the carbamate intermediate. Subsequently, the reaction would bifurcate at the intermolecular ring-closing step, which produces five-membered ring (5MR) and six-membered ring (6MR) products at the same time, thus raising a regioselectivity issue. Our calculations reveal that the outcomes of the reaction critically depend on the coordination number and the basicity of the ligands. Higher coordinate number and stronger basicity of the ligands would stabilize the 5MR transition state over the 6MR counterpart. Such a preference can be rationalized by using transition state energy decomposition. All of these results could promote the rational design of noble metal/organic base combined catalysts with higher selectivity.

Mechanistic study on ligand-controlled copper-catalyzed regiodivergent silacarboxylation of allenes with carbon dioxide and silylborane

The origin of ligand-controlled copper-catalyzed regiodivergent silacarboxylation was rationalized.

Cs2CO3 as a source of carbonyl and ethereal oxygen in a Cu-catalysed cascade synthesis of benzofuran [3,2-c] quinolin-6[5-H]ones

Simultaneous construction of C–C, C–O, and C–N bonds utilizing Cs₂CO₃ as a source of carbonyl (CO) and ethereal oxygen and a cascade synthesis of benzofuro[3,2-c]quinolin-6(5H)-one are achieved using a combination of Cu(OAc)₂ and Ag₂CO₃.

DFT studies on the mechanism of alcohol oxidation by the (bpy)CuI-TEMPO/NMI catalytic system

The oxidation of alcohol to acetaldehyde catalyzed by (bpy)Cu^I-TEMPO/NMI is investigated by the density functional method. On the basis of the studied catalytic cycle, a possible mechanism is presented to explain the experimental observations.