One-Pot Synthesis of N,N′-dialkylureas via Carbonylation of Amines with CO2 Applying Y0.08Zr0.92O1.96 Mixed Oxide (YSZ-8) as a Heterogeneous Catalyst

Abstract

Abstract:One-pot synthesis of N,N -dialkylureas were successfully achieved from catalytic carbonylation of aliphatic primary amines with CO 2 as the carbon source and Y 0.08 Zr 0.92 O 1.96 mixed oxide (Yttria-stabilized zirconia, YSZ-8) as the heterogeneous catalyst. The yield of the target product was obtained up to 80.60% from a 48 h reaction with an aliphatic primary amine and 3.0 MPa CO 2 in N-methyl-2-pirrolidinone at 160 • C. A multi-pronged mechanistic study was carried out where factors that might influence the reaction efficiency were studied, including catalyst structure, substrates basicity, CO 2 pressure, solvent polarity and reaction time. The presence of oxygen vacancies in YSZ-8 was found to be essential for the carbonylation process by creating additional reduction potential for the activation of CO 2 which would lead to the key intermediate species.

Azo‐Bridged Cesium Salt of Phenolate/Triazolide as an Unprecedented Carboxylation Catalyst for 1,3‐Disubtituted Ureas from CO2 and Amines

“…Among them, NMP is considered as the most preferable solvent for the carboxylation reaction to deliver 92.5% yield of 1,3-dihexylurea (1,3-DHU) due to its capability to trap CO 2 as well as its ability to stabilize the ionic intermediates (entry 12). [43,44] In contrast to NMP, alcohol solvents such as MeOH and 2-propanol (IPA), would reduce the basicity of the amines, and tend to compete with the amines for the nucleophilic attack to form carbamic acid intermediate during the reaction, [45] thus retarding the carboxylation process (entries 6 and 7). It is found that 13.2% yield of 1,3-DHU is achieved even in the absence of catalyst under identical conditions, showing that NMP solvent itself is able to promote the carboxylation reaction to some extent (entry 8).…”

Photothermal Cocatalytic Carbonylation of Isobutyl Amine with CO2 over Bi2O3 Polymorphs under Visible-Light Irradiation

“…Regretfully, the high thermodynamic stability and kinetic inertness of the CO 2 molecule, compared to the relatively easy absorption and of capture CO 2 by amines, has hindered the synthesis of N , N ′-dialkylurea by the catalytic carbonylation of amines with CO 2 , especially with regard to the harsh reaction conditions required such as high temperature and high pressure. As a consequence, a series of efficient catalysts of thermal activation of CO 2 , including K-doped-δ-MnO 2 , MnO 2 , , Y 2 O 3 –ZrO 2 , CeO 2 , KOH/PEG, KOH, [bmim]­OH, Y 2 (C 2 O 4 ) 3 , Co­(acac) 3 , K 3 PO 4 , CsCO 3 , Sn–Ni–O, and 1,5-diazabicyclo[4.3.0]­non-5-ene (DBU) etc., have been developed and reported over the past ten years or so. Nevertheless, despite the progress being made in speeding up the reaction rate of the carbonylation of CO 2 with amine to produce N , N ′-dialkylurea, the desired advantages of green and low-carbon economies involved in the reaction have not been fully realized due to the harsh reaction conditions.…”