A Simple Zinc Catalyst for Carbamate Synthesis Directly from CO₂

Abstract

Several zinc salts were employed as catalysts for the synthesis of carbamates directly from aromatic amines, CO , and silicate esters. Zn(OAc) offered the best performance among the salts tested. The addition of an N-donor ligand such as 1,10-phenanthroline increased the yield. The best catalytic performance of Zn(OAc) can be explained by carboxylate-assisted proton activation. The interaction between the substrate and the catalyst can be observed by chemical shifts in H and N NMR spectra. Isocyanate was a key intermediate, which was generated from amine and CO . Silicate ester was finally converted to siloxane, which was determined by Si NMR. The commercially available catalyst system could be reused. The yield of isolated carbamate could reach up to 96 % with various substrates, and the catalytic reaction was amine-selective in the presence of other functional groups.

CO2 Conversion with Alcohols and Amines into Carbonates, Ureas, and Carbamates over CeO2 Catalyst in the Presence and Absence of 2‐Cyanopyridine

“…In particular, the reactivity of anilines is generally low, which is due to the low nucleophilicity and basicity. [33] Scheme 5 shows the results of the synthesis of cyclic ureas from CO 2 + diamines. [34] Various diamines reacted with CO 2 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 to give the corresponding five-membered ring amines in high yield, which can be higher than that of non-cyclic ureas from CO 2 + amines (Scheme 4), which can be explained by the stability of the five-membered ring ureas.…”

Catalytic Conversion of Carbon Dioxide through C-N Bond Formation

“…Gratifyingly, the corresponding methyl N -phenylcarbamate was formed in a yield of 80% along with N′ -diphenylurea as by-product. Recently, they found that silicate ester (i.e., Si(OR) 4 ) could be incorporated with aliphatic or aromatic amines and CO 2 to synthesize N -arylcarbamate (Scheme 19b) [107]. Notably, the corresponding carbamates of aromatic amines could be obtained in a yield of up to 96%.…”

Supported Porous Nanomaterials as Efficient Heterogeneous Catalysts for CO2 Fixation Reactions

“…Very recently Zhang et al . reported the synthesis of a wide range of ethers using aromatic/aliphatic amines and CO 2 under pressure in the presence of Lewis acidic Zn II salts as catalyst in the presence of silicon alkoxide as an alkoxide‐donating agent to the carbamate intermediate.…”

“…[64] 2.7. Synthesis of esters, carbamates, ureas, and lactones Very recently Zhang et al [65] reported the synthesis of aw ide range of ethers using aromatic/aliphatic amines and CO 2 under pressure in the presence of Lewis acidic Zn II salts as catalyst in the presence of silicon alkoxide as an alkoxide-donating agent to the carbamate intermediate. The isolated yield of various carbamatee sters could reach 80-96 %u nder the reaction conditions used with several Zn catalysts.…”