Synthesis Of Carbamates Research Articles

Copper-catalyzed carbonylation of anilines by diisopropyl azodicarboxylate for the synthesis of carbamates

Herein, a simple Cu-catalyzed system for the synthesis of carbamates has been developed using anilines with diisopropyl azodicarboxylate as a carbonyl source under solvent-free conditions.

Heterobimetallic dinuclear lanthanide alkoxide complexes as acid–base bifunctional catalysts for synthesis of carbamates under solvent-free conditions

Heterobimetallic dinuclear lanthanide alkoxide complexes Ln2Na8(OCH2CH2NMe2)12(OH)2 [Ln: I (Nd), II (Sm), III (Yb) and IV (Y)] were used as efficient acid–base bifunctional catalysts for the synthesis of carbamates and the N-Boc protection of amines.

Oxidative Cleavage of C2–C3 Bond in Isatin Using (Diacetoxyiodo)benzene: A Facile Synthesis of Carbamates of Alkyl Anthranilates

On reaction with (diacetoxyiodo)benzene, isatin and <i>N</i>-acetyl isatin undergo the oxidative C2–C3 bond cleavage to form carbamates of alkyl anthranilates and alkyl 2-acetamidobenzoate, respectively.

Stereodivergent Carbamate Synthesis by Selective in Situ Trapping of Organic Carbonate Intermediates.

Trans carbamates have been prepared in a diastereoselective approach by a judicious one-pot combination of organic carbonates, prepared in situ, and suitable amine reagents under appropriate reaction conditions. This unprecedented approach allows for stereodivergence from a single oxirane substrate with easy access to both cis and trans carbamate isomers with high stereoselectivity (>19:1 d.r.). Key to the control of the diastereoselective nature of the conversions that lead to the trans carbamates is the in situ formation of trans-configured oligo/polycarbonates through Al catalysis, which provides the targeted products after aminolysis. The present results demonstrate the valorization of a renewable carbon-based reagent (CO2) into new valuable scaffolds and an unusual stereocontrol exerted through carbonate intermediates. A series of control experiments support the proposed mechanistic rationale towards the trans carbamate products, which is based on the trapping of an in situ formed trans-configured oligo/polycarbonate.

Synthesis of Novel Cellulose Carbamates Possessing Terminal Amino Groups and Their Bioactivity

Cellulose phenyl carbonates are an excellent platform to synthesize a broad variety of soluble and functional cellulose carbamates. In this study, the synthesis of cellulose carbamates with terminal amino groups, namely ω-aminoethylcellulose- and ω-aminoethyl-p-aminobenzyl-cellulose carbamate, is discussed. The products are well soluble and their structures can be clearly described by NMR spectroscopy. The cellulose carbamates exhibit a bactericide and fungicide activity in vitro. The ω-aminoethylcellulose carbamate possesses a strong activity against Candida albicans and Staphylococcus aureus (IC50 of 0.02 mg mL(-1) and 0.05 mg mL(-1)). The antimicrobial activity and cytotoxicity can be improved by p-amino-benzylamine (ABA) as an additional substituent. The mixed cellulose carbamate exhibits a high biocompatibility (LC50 of 3.18 mg mL(-1)) and forms films on cotton and PES, which exhibit a strong activity against S. aureus and Klebsiella pneumoniae.

Copper nanoparticles on charcoal: an effective nanocatalyst for the synthesis of enol carbamates and amides via an oxidative coupling route

The catalytic activity of copper nanoparticles on charcoal (Cu/C) was investigated as an environmentally friendly heterogeneous catalyst for the synthesis of enol carbamates and amides via the oxidative coupling of N,N-dialkyl formamides with 1,3-dicarbonyl compounds and aromatic aldehydes with amine hydrochloride salts, respectively. Various enol carbamates and amides were synthesized in moderate to good yields using this method. Moreover, the catalyst could be recovered and subsequently reused in further reactions.

Synthesis of kenaf cellulose carbamate and its smart electric stimuli-response

Cellulose carbamate (CC) was produced from kenaf core pulp (KCP) via a microwave reactor-assisted method. The formation of CC was confirmed by Fourier transform infrared spectroscopy and nitrogen content analysis. The degree of substitution, zeta potential and size distribution of CC were also determined. The CC was characterized with scanning electron microscopy, X-ray diffraction and thermogravimetry analysis. The CC particles were then dispersed in silicone oil to prepare CC-based anhydrous electric stimuli-responsive electrorheological (ER) fluids. Rhelogical measurement was carried out using rotational rheometer with a high voltage generator in both steady and oscillatory shear modes to examine the effect of electric field strength on the ER characteristics. The results showed that the increase in electric field strength has enhanced the ER properties of CC-based ER fluid due to the chain formation induced by electric polarization among the particles.

ChemInform Abstract: N‐Substituted Carbamate Synthesis Using Urea as Carbonyl Source over TiO2—Cr2O3/SiO2 Catalyst.

AbstractTiO2—Cr2O3/SiO2 catalyzes the synthesis of N‐substituted carbamates using urea as carbonyl source.

ChemInform Abstract: Synthesis of Sulfoximine Carbamates by Rhodium‐Catalyzed Nitrene Transfer of Carbamates to Sulfoxides.

Sulfoximines are of considerable interest for incorporation into medicinal compounds. A convenient synthesis of N-protected sulfoximines is achieved, under mild conditions, by rhodium-catalyzed transfer of carbamates to sulfoxides. The first examples of 4-membered thietane-oximines are prepared. Sulfoximines bearing Boc and Cbz groups are stable to further cross coupling reactions, and readily deprotected. This method may facilitate the preparation of NH-sulfoximines providing improved (global) deprotection strategies, which is illustrated in the synthesis of methionine sulfoxide (MSO).

Solvent‐Free Iridium‐Catalyzed Reactivity of CO2 with Secondary Amines and Hydrosilanes

AbstractThe complex [Ir(H)(CF3SO3)(NSiN)(coe)] (NSiN=bis(pyridine‐2‐yloxy)methylsilyl fac‐coordinated) (1) is an effective catalyst precursor for the solvent‐free synthesis of silyl carbamates from reaction of aliphatic secondary amines with CO2 and HSiMe(OSiMe3)2. The preferential formation of the silyl carbamate instead of the expected formamide or methylamine has proven to be consequence of an iridium‐catalyzed dehydrogenative Si−N coupling between the silane and the amine to afford the corresponding silyl amine, which under the reaction conditions reacts with CO2 to give the corresponding silyl carbamate.

Mechanochemical 1,1′-Carbonyldiimidazole-Mediated Synthesis of Carbamates

1,1′-Carbonyldiimidazole (CDI) was used as an eco-friendly acylation agent for the mechanochemical preparation of carbamates. The anticonvulsant N-methyl-O-benzyl carbamate was obtained in a vibrational ball-mill, while planetary ball-mill was suitable to develop a new sustainable method to access N-protected amino esters with no racemization. Compared to the synthesis in solution, mechanochemistry proved to be a powerful tool enhancing the reactivity of both alcohol and carbamoyl-imidazole intermediate, under mild conditions, without the need of activation as usually reported for solution synthesis. This new technology provides a sustainable method for the synthesis of carbamates using 1,1′-carbonyldiimidazole.

Base-promoted coupling of carbon dioxide, amines, and diaryliodonium salts: a phosgene- and metal-free route to O-aryl carbamates.

A phosgene- and metal-free synthesis of O-aryl carbamates is realized through a three-component coupling of carbon dioxide, amines and diaryliodonium salts. The reaction only requires a base as the promoter, providing access to a diverse array of O-aryl carbamates in moderate to high yields with excellent chemoselectivity.

Anchoring of a Copper(II)–Schiff Base Complex onto Silica-Coated Ferrite Nanoparticles: A Magnetically Separable Catalyst for Oxidative C–O Coupling by Direct C(sp2)–H and C(sp3)–H Bond Activation

A novel catalyst consisting of a Schiff base–copper complex on surface-modified silica-coated ferrite nanoparticles was been prepared and used for oxidative C–O cross-coupling reactions of 1,3-dicarbonyl compounds with formamides for the synthesis of enol carbamates. The new catalyst has also been used for esterification of alkylbenzenes with cyclic ethers.

ChemInform Abstract: Copper‐Catalyzed Intermolecular C(sp3)—H Bond Functionalization Towards the Synthesis of Tertiary Carbamates.

We describe the development of an intermolecular unactivated C(sp3)–H bond functionalization towards the direct synthesis of tertiary carbamates. The transformation proceeded using a readily available, abundant first-row transition metal catalyst (copper), and isocyanates as the source of the amide moiety. This is a novel strategy for direct transformation of a variety of unactivated hydrocarbon feedstocks to N-alkyl-N-aryl and N,N-dialkyl carbamates without pre-functionalization or installation of a directing group. The reaction had a broad substrate scope with 3° > 2° > 1° site selectivity. The reaction proceeded even on a gram scale, and a corresponding free amine was directly obtained when the reaction was performed at high temperature. Kinetic studies suggested that radical-mediated C(sp3)–H bond cleavage was the rate-determining step.

ChemInform Abstract: Synthesis of Acyl Carbamates via Four Component Pd‐Catalyzed Carbonylative Coupling of Aryl Halides, Potassium Cyanate, and Alcohols.

AbstractThe reactions are carried out in a two chamber system, generating CO from COgen in the first chamber.

One pot synthesis of ureas and carbamates via oxidative carbonylation of aniline-type substrates by CO/O2 mixture catalyzed by Pd-complexes

Carbonylation of aromatic amines by direct insertion of carbon monoxide is catalyzed by PdCl2(XnPy)2 complexes (where Py=pyridine, X=−CH3, −Cl; n=0–2) and gives, depending on the conditions, ethyl N-phenylcarbamates or N,N′‑diphenylureas. For carbonylation of aniline, a proper choice of XnPy ligands in PdCl2(XnPy)2 catalyst and application of molecular oxygen instead of nitrobenzene (conventionally used oxidant for carbonylations) allow to carry out the process under mild conditions with high yield and selectivity. The best results (75% yield of the main product with selectivity of catalyst above 90%) were obtained for the process catalyzed by PdCl2(2,4-Cl2Py)2 complex at 100°C and they were greatly improved in comparison to 41% yield and 68% selectivity obtained for CO/nitrobenzene used at 180°C.

ChemInform Abstract: Base‐Promoted Coupling of Carbon Dioxide, Amines, and N‐Tosylhydrazones: A Novel and Versatile Approach to Carbamates.

AbstractA novel and versatile reaction of CO2 with N‐tosylhydrazones and amines is developed providing an attractive method for the straightforward synthesis of various carbamates.

Synthesis of 3,3,3-trifluoroethyl isocyanate, carbamate and ureas. Anticancer activity evaluation of N-(3,3,3-trifluoroethyl)-N'-substituted ureas.

A new method is described for producing 3,3,3-trifluoroethyl isocyanate from perfluoroisobutene (PFIB). Isocyanate was used for synthesis of carbamates and ureas. A series of trifluoroethyl-substituted ureas has been tested in the National Cancer Institute (NCI, Bethesda, USA) by the NCI-60 DTP Human Tumor Cell Line Screening Program at a single high dose (10-5 M). The moderate anticancer activity was shown against some types of cancer on the individual human cell lines for leukemia, non-small cell lung cancer and renal cancer.

Synthesis of Sulfoximine Carbamates by Rhodium-Catalyzed Nitrene Transfer of Carbamates to Sulfoxides.

Sulfoximines are of considerable interest for incorporation into medicinal compounds. A convenient synthesis of N-protected sulfoximines is achieved, under mild conditions, by rhodium-catalyzed transfer of carbamates to sulfoxides. The first examples of 4-membered thietane-oximines are prepared. Sulfoximines bearing Boc and Cbz groups are stable to further cross coupling reactions, and readily deprotected. This method may facilitate the preparation of NH-sulfoximines providing improved (global) deprotection strategies, which is illustrated in the synthesis of methionine sulfoxide (MSO).

Improved Synthesis of Cellulose Carbamates with Minimum Urea Based on an Easy Scale-up Method

Cellulose carbamates (CCs) were successfully prepared from cellulose/urea (CU) mixtures based on an easy scale-up method and minimum urea. Urea content and the reaction conditions on the nitrogen content of the reacted CU (RCU) mixtures and CCs were systematically investigated. RCU mixtures and CCs were characterized with elemental analysis, Fourier transform infrared spectroscopy, X-ray diffraction, NMR spectrometry and solubility testing. The result indicated that almost all of urea was involved in the derivatization reaction and cellulose was converted into CC with absence of byproducts. The nitrogen content of CCs increased with an increase of the urea content and the reaction temperature, as well as the reaction time. CCs retained the cellulose I crystalline, and the degree of polymerization hardly changed with the reaction conditions. CCs prepared from CU mixtures with the urea content of 3.4–4.6 wt % displayed good solubility in NaOH/ZnO aqueous solutions. Especially, RCU mixtures without washing c...