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

Catalytic Enantioselective Transfer Hydrogenation-Carboxylative Cyclization to 4-Fluoroalkyl 2-Oxazolidinone with CO2 as the C1 Synthon

We report a sequential catalytic asymmetric transfer hydrogenation-carboxylative cyclization for the facile construction of chiral 4-fluoroalkyl 2-oxazolidinones with high enantioselectivity. The resulting 2-oxazolidinones can be easily elaborated to synthetic useful chiral β-fluoroalkyl β-amino alcohols. This research also represents a rare example of catalytic asymmetric sequential reactions using CO₂ as a C1 synthon as well as carboxylative cyclization of α-fluoroalkyl propargylamines.

Recent Advances in the Chemical Fixation of Carbon Dioxide: A Green Route to Carbonylated Heterocycle Synthesis

Carbon dioxide produced by human activities is one of the main contributions responsible for the greenhouse effect, which is modifying the Earth’s climate. Therefore, post-combustion CO2 capture and its conversion into high value-added chemicals are integral parts of today’s green industry. On the other hand, carbon dioxide is a ubiquitous, cheap, abundant, non-toxic, non-flammable and renewable C1 source. Among CO2 usages, this review aims to summarize and discuss the advances in the reaction of CO2, in the synthesis of cyclic carbonates, carbamates, and ureas appeared in the literature since 2017.

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.

Reactions of secondary propargylamines with heteroallenes for the synthesis of diverse heterocycles

This focused review aims to summarize recent developments in the processes involving additions of secondary propargylamines to various heteroallenes and subsequent transition metal-catalyzed or electrophile-mediated cyclizations.