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We have successfully isolated and characterized the zinc carbamate complex (phen)Zn(OAc)(OC(=O)NHPh) (1; phen=1,10‐phenanthroline), formed as an intermediate during the Zn(OAc)2/phen‐catalyzed synthesis of organic carbamates from CO2, amines, and the reusable reactant Si(OMe)4. Density functional theory calculations revealed that the direct reaction of 1 with Si(OMe)4 proceeds via a five‐coordinate silicon intermediate, forming organic carbamates. Based on these results, the catalytic system was improved by using Si(OMe)4 as the reaction solvent and additives like KOMe and KF, which promote the formation of the five‐coordinated silicon species. This sustainable and effective method can be used to synthesize various N‐aryl and N‐alkyl carbamates, including industrially important polyurethane raw materials, starting from CO2 under atmospheric pressure. [ABSTRACT FROM AUTHOR]

New sustainable approaches should be developed to overcome equilibrium limitation of dialkyl carbonate synthesis from CO2 and alcohols. Using tetraethyl orthosilicate (TEOS) and CO2 with Zr catalysts, we report the first example of sustainable catalytic synthesis of diethyl carbonate (DEC). The disiloxane byproduct can be reverted to TEOS. Under the same conditions, DEC can be synthesized using a wide range of alkoxysilane substrates by investigating the effects of the number of ethoxy substituent in alkoxysilane substrates, alkyl chain, and unsaturated moiety on the fundamental property of this reaction. Mechanistic insights obtained by kinetic studies, labeling experiments, and spectroscopic investigations reveal that DEC is generated via nucleophilic ethoxylation of a CO2‐inserted Zr catalyst and catalyst regeneration by TEOS. The unprecedented transformation offers a new approach toward a cleaner route for DEC synthesis using recyclable alkoxysilane. [ABSTRACT FROM AUTHOR]

The combination catalyst of CeO2 and H-FAU zeolite was effective for the direct synthesis of diethyl carbonate from CO2 and ethanol with 2,2-diethoxypropane as a dehydrating regent, where H-FAU catalyzed hydrolysis of 2,2-diethoxypropane. The combination catalyst provided high activity and a high diethyl carbonate yield of 72% based on 2,2-diethoxypropane at a low temperature of 393 K. [ABSTRACT FROM AUTHOR]

Amines, carbon dioxide fixation, density functional calculations, sustainable chemistry, zinc Cover Feature: N-Aryl and N-Alkyl Carbamates from 1 Atmosphere of CO2 (Chem. Eur. J. 72/2021) Keywords: amines; carbon dioxide fixation; density functional calculations; sustainable chemistry; zinc EN amines carbon dioxide fixation density functional calculations sustainable chemistry zinc 17974 17974 1 12/27/21 20211223 NES 211223 B We have successfully isolated b the zinc carbamate complex (phen)Zn(OAc)(OC(=O)NHPh) ( B 1 b , phen=1,10-phenanthroline), which is an intermediate in the Zn(OAc) SB 2 sb /phen-catalyzed synthesis of organic carbamates from CO SB 2 sb , amines, and Si(OMe) SB 4 sb . [Extracted from the article]

A heterogeneous zirconium catalyst was grafted on a ceria‐coated silica support, denoted as Zr(OEt)x/CeO2/SiO2. It exhibited higher catalytic activity compared to its homogeneous counterpart, Zr(OEt)4, in the conversion of carbon dioxide to diethyl carbonate using tetraethyl orthosilicate as a regenerable agent in the absence of any dehydrating agents under non‐protic conditions. We found that the ceria‐coated silica (CeO2/SiO2) support not only improved the catalytic activity of Zr(OEt)4 but also inhibited catalyst deactivation during catalyst recycling tests. Furthermore, we analyzed the surface of the Zr(OEt)x/CeO2/SiO2 catalysts by FE‐SEM and EDX. [ABSTRACT FROM AUTHOR]

We have successfully isolated and characterized the zinc carbamate complex (phen)Zn(OAc)(OC(=O)NHPh) (1; phen=1,10‐phenanthroline), formed as an intermediate during the Zn(OAc)2/phen‐catalyzed synthesis of organic carbamates from CO2, amines, and the reusable reactant Si(OMe)4. Density functional theory calculations revealed that the direct reaction of 1 with Si(OMe)4 proceeds via a five‐coordinate silicon intermediate, forming organic carbamates. Based on these results, the catalytic system was improved by using Si(OMe)4 as the reaction solvent and additives like KOMe and KF, which promote the formation of the five‐coordinated silicon species. This sustainable and effective method can be used to synthesize various N‐aryl and N‐alkyl carbamates, including industrially important polyurethane raw materials, starting from CO2 under atmospheric pressure. [ABSTRACT FROM AUTHOR]

Dialkyl carbonates (DRCs) are valuable compounds widely used in the industry. The synthesis of DRC from CO 2 has attracted interest as an alternative to the current method, which uses phosgene. However, the reported approaches for DRC synthesis from CO 2 requires high-pressure and high-concentration CO 2 , resulting in elevated costs associated with CO 2 purification and manufacturing facilities. In this report, we present an environmentally friendly method for producing DRC from low-concentration and low-pressure CO 2 via a dehydration condensation approach without the use of halogenated alkylating agents. This method involves the formation of monoalkyl carbonate [BASE-H][ROC(O)O] using a strong organic base and alcohols, tetraalkyl orthosilicates as dehydrating agents, and CeO 2 as the catalyst. Using the method, 39 and 30% of diethyl carbonate yields were accomplished with only 100 and 15 vol % CO 2 (CO 2 /N 2 = 15:85) gas bubbling at atmospheric pressure, even under reaction conditions with no large excess of either CO 2 , alcohol, or dehydration agent., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Herein, we report the direct conversion of low-concentration CO 2 (15 vol %), equivalent to the CO 2 concentration in the exhaust gas from a thermal power station, into carbamic acid esters (CAEs), which are precursors for pharmaceuticals, agrochemicals, and isocyanates. The reaction was performed using Si(OMe) 4 as a nonmetallic regenerable reagent and 1,8-diazabicyclo[5.4.0]undec-7-ene as a CO 2 capture agent and catalyst. This reaction system does not require the addition of metal complex catalysts or metal salt additives and is therefore simpler than our previously reported reaction system involving Ti(OR) 4 and a Zn(II) catalyst. A variety of N -aryl, N -alkyl, and bis CAEs (precursors of polyurethane raw materials) were obtained in moderate to high yields (45-77% for 6 examples, 84-89% for 7 examples). In addition, bis CAEs were successfully synthesized from simulated exhaust gas containing impurities such as SO 2 , NO 2 , and CO or on a gram scale. We believe that this method can eliminate the use of toxic phosgene as the raw material for isocyanate production and mitigate CO 2 emissions.

We have successfully isolated and characterized the zinc carbamate complex (phen)Zn(OAc)(OC(=O)NHPh) (1; phen=1,10-phenanthroline), formed as an intermediate during the Zn(OAc) 2 /phen-catalyzed synthesis of organic carbamates from CO 2 , amines, and the reusable reactant Si(OMe) 4 . Density functional theory calculations revealed that the direct reaction of 1 with Si(OMe) 4 proceeds via a five-coordinate silicon intermediate, forming organic carbamates. Based on these results, the catalytic system was improved by using Si(OMe) 4 as the reaction solvent and additives like KOMe and KF, which promote the formation of the five-coordinated silicon species. This sustainable and effective method can be used to synthesize various N-aryl and N-alkyl carbamates, including industrially important polyurethane raw materials, starting from CO 2 under atmospheric pressure., (© 2021 Wiley-VCH GmbH.)