Polymer- and Carbon Nanotube-Supported Heterogeneous Catalysts for the Synthesis of Carbamates from Halides, Amines, and CO2

Abstract

A series of tetraalkylammonium catalysts immobilized on polystyrene or carbon nanotubes were investigated in a reaction between alkyl halides, amines, and CO 2 . The yield of carbamates was up to 85 % at 100°C and 1 MPa of CO 2 after 3 h (first stage 25°C, 1 h) in the presence of Cs 2 CO 3 and DMF as a solvent. The best results were achieved in the case of large ammonium substituents (C 4 and C 6 ) in the catalyst, benzyl amine, and benzyl chloride as reagents. The catalysts retained their activity after at least five cycles when carefully dried between cycles. Both polymer and carbon nanotube supports were equally effective, but the latter were less prone to deactivation. Graphical Abstract

Advanced zeolite and ordered mesoporous silica-based catalysts for the conversion of CO2to chemicals and fuels

“…In the absence of a catalyst, the amine alkylation also occurs and constitutes the main side product. To minimize undesired reaction, different catalysts have been used such as base catalysts (DBU, alkali metal salts), [260][261][262][263][264] alkyl-onium salts 265,266 and metal based catalysts (Pd, Zn). 263,267 In the literature, only few examples describing the use of OMS based catalysts was reported.…”

CO2‐Based Carbamate Synthesis Utilizing Reusable Polymer‐Supported DBU

“…The well-known three-component coupling reaction involving amines, CO 2 , and alkyl halides has become a primary strategy. [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] This approach leverages CO 2 as a precursor for carbamate synthesis, offering an environ-mentally sound alternative to problematic reagents like alkyl chloroformates (derived from phosgene). This substitution not only promotes sustainability and environmental friendliness but also addresses challenges associated with the toxicity and handling of alkyl chloroformates.…”

“…[38] Cs 2 CO 3 was also employed as a base in this three-component coupling reaction, sometimes necessitating high temperatures and extended reaction times, in combination with tetrabutylammonium iodide as an additive and DMF as a solvent. [39] In 2016, Krawczyk's group [40] developed a similar protocol for carbamate synthesis from amines, alkyl halides, and CO 2 , using tetraalkylammonium catalysts immobilized on polystyrene or carbon nanotubes. While tetraalkylammonium salts can be recycled, this protocol still requires high pressure to achieve satisfactory carbamate yields, and by-products are produced.…”

Pd Nanoparticles and Mixture of CO2/CO/O2 Applied in the Carbonylation of Aniline

“…Despite limited number of applications of CO 2 in organic synthesis caused mainly by high kinetic inertness and thermodynamic stability of CO 2 [21][22][23][24], every year new approaches involving CO 2 have been investigated [25][26][27][28]. For many years, carbonylation of aromatic amines by CO 2 was poorly represented in the literature, in contrast to carbonylation of ammonia and aliphatic amines by CO 2 [29][30][31][32][33][34]. Perhaps, lower nucleophilicity of nitrogen atom in the aromatic ring of aromatic amines decreases their reactivity towards CO 2 [5].…”