Thermal-reductive transformations of carbon dioxide catalyzed by small molecules using earth-abundant elements

Abstract

In the present review, we summarize the progress for thermal reductive transformations of CO 2 catalyzed by small homogeneous catalysts using earth-abundant elements. Three main types of transformations categorized by the use of different reductants (hydrogen, hydrosilanes, and boranes), in which no C-C bond formation is involved, are surveyed.

Delineation of the Critical Parameters of Salt Catalysts in the N‐Formylation of Amines with CO2

“…Under standardized reaction conditions (10 mol %c atalyst, 1bar CO 2 ,2 58C, 6h,s olvent-free) with N-methylaniline as the substrate, 1-butyl-3-methylimidazoliumc hloride ([BMIm]Cl), the prototypeI Lc atalyst reported for this reaction, [10] afforded the N-methylformanilide product in 3% yield ( [15][16][17][18][19][20]. In DMSO,t he highest polarity solvent tested, almost no differences can be seen among the chlorides alts tested with N-methylformanilide yields being around 55 %( Ta bleS1).…”

“…[10] It was proposed that the nucleophilicity of the anion activates the hydrosilane reducing agent enabling the reduction of CO 2 [9,11,17] or,m ore recently,I Ls were shown to act as ab ase duringc arbamatea ssisted activation (vide infra). [10] It was proposed that the nucleophilicity of the anion activates the hydrosilane reducing agent enabling the reduction of CO 2 [9,11,17] or,m ore recently,I Ls were shown to act as ab ase duringc arbamatea ssisted activation (vide infra).…”

“…ILs and other simple salts were shown to be efficient catalysts for the N‐formylation of amines employing CO 2 as a C1 source in combination with hydrosilane reducing agents (Scheme ) . It was proposed that the nucleophilicity of the anion activates the hydrosilane reducing agent enabling the reduction of CO 2 or, more recently, ILs were shown to act as a base during carbamate assisted activation (vide infra) . In both cases, the activity of the salt predominantly depends on the nature of the anion with a well‐defined trend in the halide series being I − <Br − <Cl − ≪F − .…”

Scalable direct N-methylation of drug-like amines using 12CO2/13CO2 by simple inorganic base catalysis

“…1a) [8]. However, in spite of the tremendous progress in the field of direct chemical utilization of CO 2 in organic reactions [9][10][11][12][13][14][15], development of synthetic protocol with a general applicability to complex drug-like compounds ubiquitous in pharmaceutical industry remains a significant challenge [16].…”

Recent Advances of CO2 Fixation via Asymmetric Catalysis for the Direct Synthesis of Optically Active Small Molecules

“…[24][25][26] Physical energy such as light or electricity was also employed to solve the issues brought by thermodynamic stability of CO 2 . [27][28] However, these traditional methods usually require multi-steps, resulting in waste or undesirable by-products.…”