Synthesis Of Carbamates Research Articles

SYNTHESIS AND REACTIONS OF SOME NEW MORPHOLINYLPYRROLYL TETRAHYDROTHIENO[2,3-c] ISOQUINOLINE

Hydrazinolysis of ethyl-5-morpholin-4-yl-1-(1H-pyrrol-1-yl)-6,7,8,9-tetrahydrothieno[2,3-c]iso- quinoline-2-carboxylate afforded the corresponding carbo- hydrazide which upon condensation with aromatic aldehydes, acetyl acetone and/ or carbon disulfide gave N- arylidinecarbohydrazide, dimethylpyrazolyl methanone, [1,3,4]oxadiazole-2-thiol and its ethyl ester derivatives respectively. Diazotization of the carbohydrazide with nitrous acid afforded the corresponding carboazide which was used for synthesis of carbamates and substituted carboxamides. Boiling of the carboazide in dry xylene afforded the pyrazinone compound which was used for synthesis of other heterocycles containing pyrrolopyrazinothinoisoquinoline moeity.

HBF4·OEt2: An efficient fluorinated acid catalyst for the one-pot synthesis of secondary and tertiary N-homoallylic carbamates

An efficient method for the one-pot synthesis of secondary and tertiary N-homoallylic carbamates using catalytic amount of HBF4·OEt2 is described. The reaction proceeded smoothly to afford the corresponding N-homoallylic carbamates in good to high yields. Operationally simple and easily scalable features make this method more practical over existing methods. Use of HBF4·OEt2 as an acid catalyst also proves the catalytic activity of fluorinated acid catalyst in this important organic transformation.

ChemInform Abstract: Synthesis of Fluorous Photolabile Aldehyde and Carbamate and Alkyl Carbamate Protecting Groups for Carbohydrate‐Associated Amines.

ChemInformVolume 45, Issue 19 Preparative Organic Chemistry ChemInform Abstract: Synthesis of Fluorous Photolabile Aldehyde and Carbamate and Alkyl Carbamate Protecting Groups for Carbohydrate-Associated Amines. Rajarshi Roychoudhury, Rajarshi Roychoudhury Dep. Chem., Indiana Univ., Bloomington, IN 47405, USASearch for more papers by this authorNicola L. B. Pohl, Nicola L. B. Pohl Dep. Chem., Indiana Univ., Bloomington, IN 47405, USASearch for more papers by this author Rajarshi Roychoudhury, Rajarshi Roychoudhury Dep. Chem., Indiana Univ., Bloomington, IN 47405, USASearch for more papers by this authorNicola L. B. Pohl, Nicola L. B. Pohl Dep. Chem., Indiana Univ., Bloomington, IN 47405, USASearch for more papers by this author First published: 23 April 2014 https://doi.org/10.1002/chin.201419042AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume45, Issue19May 13, 2014 RelatedInformation

Influence of Solvent on Reaction Path to Synthesis of Methyl N-Phenyl Carbamate from Aniline, CO2 and Methanol

Methyl N-phenyl carbamate (MPC), an important organic chemical, can be synthesized from aniline, CO2 and methanol. Catalyst Cu-Fe/ZrO2-SiO2 was first prepared and its catalytic performance for MPC synthesis was evaluated. Then the influence of solvent on the reaction path of MPC synthesis was investigated. It is found that the reaction intermediate is different with acetonitrile or methanol as a solvent. With acetonitrile as a solvent, the synthesis of MPC follows the reaction path with diphenyl urea as the intermediate, while with methanol as a solvent the reaction occurs via the reaction path with dimethyl carbonate as the intermediate. The catalytic mechanism of cooperative catalysis comprising metal sites, Lewis acid sites and Lewis base sites is proposed according to different reaction intermediates.

Copper-Catalyzed Oxidative Coupling of Formamides with Salicylaldehydes: Synthesis of Carbamates in the Presence of a Sensitive Aldehyde Group

A diverse library of novel carbamates was synthesized utilizing copper-catalyzed oxidative C-O coupling of formamides and salicylaldehydes. Sensitive aldehyde groups remained intact in the presence of an oxidant and a transition-metal salt. Salicylaldehydes bearing electron-donating, electron-withdrawing, and halogen groups as well as 1-hydroxy-2-naphthaldehydes provided the desired carbamates in good to excellent yields.

Synthesis of Fluorous Photolabile Aldehyde and Carbamate and Alkyl Carbamate Protecting Groups for Carbohydrate-Associated Amines

Two new fluorous photolabile-protecting groups (FNBC and FNB) and a new base-labile protecting group (FOC) for the masking of amines are reported. The protecting groups survive a wide range of common reaction conditions used in oligosaccharide synthesis and render the attached molecules amenable to fluorous solid-phase extraction (FSPE). A glycosyl acceptor containing the FNB group is shown to be useful in the synthesis of carbohydrates tagged with free deactivated secondary amines.

Synthesis of kenaf cellulose carbamate using microwave irradiation for preparation of cellulose membrane

Cellulose carbamate (CCs) was produced from kenaf core pulp (KCP) using microwave reactor-assisted method. The effects of urea concentration and reaction time on the formation of nitrogen content in CCs were investigated. The CCs’ solubility in LiOH/urea system was determined and its membranes were characterized. As the urea content and reaction time increased, the nitrogen content form in CCs increased which enhanced the CCs’ solubility. The formation of CCs was confirmed by Fourier transform infrared spectroscopy (FT-IR) and nitrogen content analysis. The CCs’ morphology was examined using Scanning electron microscopy (SEM). The cellulose II and crystallinity index of the membranes were confirmed by X-ray diffraction (XRD). The pore size of the membrane displayed upward trend with respect to the urea content observed under Field emission scanning electron microscope (FESEM). This investigation provides a simple and efficient procedure of CCs determination which is useful in producing environmental friendly regenerated CCs.

Investigation of supported Zn(OAc)2 catalyst and its stability in N-phenyl carbamate synthesis

Zn(OAc)2 was found to give excellent catalytic performance for methyl N-phenyl carbamate (MPC) synthesis from aniline and dimethyl carbonate (DMC). However, after being used for only once it tended to lose activity because of the formation of ZnO by the reaction of Zn(OAc)2 and methanol. Zn(OAc)2/SiO2 was prepared by incipient impregnation and it gave excellent catalytic performance in MPC synthesis, on which aniline conversion and MPC yield were 98.1% and 93.8%, respectively. And Zn(OAc)2/SiO2 was found to be more stable than Zn(OAc)2 during the reaction. When Zn(OAc)2/SiO2 was used for the fifth time, aniline conversion and MPC yield were found to be 64.3% and 38.1%, respectively. The Zn(OAc)2/SiO2 catalyst was characterized by TG-DTA, ICP, FTIR, XRD and XPS. The characterization results suggested that the deactivation of Zn(OAc)2/SiO2 was also due to the formation of ZnO and there were two reasons for the improved stability of Zn(OAc)2/SiO2 catalyst. One was the formation of the Si–O–Zn bonds in Zn(OAc)2/SiO2 catalyst, which increased the steric hindrance of Zn and consequently retarded the reaction between Zn(OAc)2 and methanol. The other cause was the dehydration between methanol and the hydroxyl group on the SiO2 surface, which reduced the chance of a reaction between methanol and Zn(OAc)2.

ChemInform Abstract: L‐Proline—TBAB‐Catalyzed Phosgene Free Synthesis of Methyl Carbamates from Amines and Dimethyl Carbonate.

The reaction of amines and dimethyl carbonate (DMC) in the presence of catalytic amounts of L-proline and tetrabutylammonium bromide (TBAB) afforded methyl carbamates in good to excellent yields under mild conditions. The presence of both L-proline and TBAB co-catalysts is vital for this transformation.

Metal free oxidative coupling of aryl formamides with alcohols for the synthesis of carbamates

A direct transformation of N-aryl formamides to the corresponding carbamates via the formation of isocyanate intermediates is achieved in good yields using hypervalent iodine as an oxidant.

PdCl2 catalyzed efficient assembly of organic azides, CO, and alcohols under mild conditions: a direct approach to synthesize carbamates

A simple and readily available PdCl2 catalyzed carbamate synthesis method via isocyanate generation and application in situ has been developed. This chemistry provides an efficient and practical approach to synthesize carbamates from simple organic azides, CO atmosphere and alcohols. The broad scope, mild and neutral conditions, and only N2 as the byproduct make this transformation very useful. Moreover, simple examples of modification of bioactive molecules and construction of macrocycles were achieved through this protocol.

One‐pot synthesis of methyl n‐phenyl carbamate from aniline, carbon dioxide and methanol

AbstractBACKGROUNDMethyl N‐phenyl carbamate (MPC) is an intermediate for the manufacture of methylene diphenyl diisocyanate (MDI) by a non‐phosgene route. The synthesis of MPC from aniline, carbon dioxide and methanol can transform the greenhouse gas carbon dioxide into value‐added product, MPC.RESULTSBicyclic amidine (DBU)–acetonitrile was found to be an excellent catalyst–solvent combination for MPC synthesis. Under the reaction conditions of initial pressure of carbon dioxide 1 MPa, reaction time 5 h, reaction temperature 180°C, volumetric ratio of methanol/aniline 1:4, volumetric ratio of acetonitrile/aniline 1:1, and mass percentage of DBU 5.6%, the conversion of aniline was 7.1% and the selectivity of MPC was 25.3%. A plausible catalytic reaction mechanism was proposed. The results of alkyl N‐phenyl carbamate (APC) synthesis from aniline, carbon dioxide and alcohol (methanol, ethanol, propanol or butanol) showed that the conversion of aniline and the selectivity of the corresponding APC decreased significantly with increase of the stereo hindrance on the alcohol substrate.CONCLUSIONThe reaction of aniline, carbon dioxide and alcohol to APC, especially MPC, can be achieved even though stereo hindrance on the alcohol substrate limits the reaction. © 2013 Society of Chemical Industry

Model for High-Throughput Screening of Multitarget Drugs in Chemical Neurosciences: Synthesis, Assay, and Theoretic Study of Rasagiline Carbamates

The disappointing results obtained in recent clinical trials renew the interest in experimental/computational techniques for the discovery of neuroprotective drugs. In this context, multitarget or multiplexing QSAR models (mt-QSAR/mx-QSAR) may help to predict neurotoxicity/neuroprotective effects of drugs in multiple assays, on drug targets, and in model organisms. In this work, we study a data set downloaded from CHEMBL; each data point (>8000) contains the values of one out of 37 possible measures of activity, 493 assays, 169 molecular or cellular targets, and 11 different organisms (including human) for a given compound. In this work, we introduce the first mx-QSAR model for neurotoxicity/neuroprotective effects of drugs based on the MARCH-INSIDE (MI) method. First, we used MI to calculate the stochastic spectral moments (structural descriptors) of all compounds. Next, we found a model that classified correctly 2955 out of 3548 total cases in the training and validation series with Accuracy, Sensitivity, and Specificity values>80%. The model also showed excellent results in Computational-Chemistry simulations of High-Throughput Screening (CCHTS) experiments, with accuracy=90.6% for 4671 positive cases. Next, we reported the synthesis, characterization, and experimental assays of new rasagiline derivatives. We carried out three different experimental tests: assay (1) in the absence of neurotoxic agents, assay (2) in the presence of glutamate, and assay (3) in the presence of H2O2. Compounds 11 with 27.4%, 8 with 11.6%, and 9 with 15.4% showed the highest neuroprotective effects in assays (1), (2), and (3), respectively. After that, we used the mx-QSAR model to carry out a CCHTS of the new compounds in >400 unique pharmacological tests not carried out experimentally. Consequently, this model may become a promising auxiliary tool for the discovery of new drugs for the treatment of neurodegenerative diseases.

ChemInform Abstract: Chloroformate Free, Scalable Approach for the Synthesis of Organic Carbamates and Their Alkylation.

AbstractThe synthesis of carbamates of 2‐aminopyridine is described, avoiding the employment of hazardous chloroformate reagents.

ChemInform Abstract: Palladium‐Catalyzed Synthesis of N‐Aryl Carbamates.

An efficient synthesis of aryl carbamates was achieved by introducing alcohols into the reaction of palladium-catalyzed cross-coupling of ArX (X = Cl, OTf) with sodium cyanate. The use of aryl triflates as electrophilic components in this transformation allowed for an expanded substrate scope for direct synthesis of aryl isocyanates. This methodology provides direct access to major carbamate protecting groups, S-thiocarbamates, and diisocyanate precursors to polyurethane materials.

Organic Syntheses with Photochemically Generated Chemicals from Tetrachloroethylene

AbstractChlorine, phosgene, and trichloroacetyl chloride are some of the complex mixture of multiple products that is obtained from the oxidative photodecomposition of tetrachloroethylene. These toxic but important reagents in organic synthesis can generated and used in situ for practical syntheses of ureas, amides, carbonates, esters, carbamates, enaminones, and organochlorides.

Reactivity of Hydroxy and Amino Derivatives of 2-Phenyl-1H-imidazoline and 2-Phenyl-1H-imidazole toward Isocyanates: Synthesis of Appropriate Carbamates and Ureas

Reactivity of 2-(4-hydroxyphenyl)-1H-imidazoline and 2-(4-hydroxyphenyl)-1H-imidazole toward substituted phenyl isocyanates was studied. When mentioned imidazoline was treated with 2.5 equiv of substituted phenyl isocyanate, three N,O-dicarboxamides were prepared (substituents are H, 4-NO2, and 4-CH3). Subsequently, N,O-diacetylated 2-(4-hydroxyphenyl)-1H-imidazoline was prepared and selective deprotection method was developed for preparation of 1-acetyl-2-(4-hydroxyphenyl)-1H-imidazoline using diethylamine in acetone. Six carbamates derived from this imidazoline were then prepared using 1.1 equiv of substituted phenyl isocyanates (substituents are H, 4-CH3, 4-OCH3, 4-NO2, 4-CN, and 3-CF3). Finally, two carbamates were prepared from 2-(4-hydroxyphenyl)-1H-imidazole (substituents are 4-NO2 and 4-CN). No reactivity to imidazole ring was observed in this case. Eight derivatives were subjected to antimycobacterial screening. Concurrently, reactivity of 2-(2-aminophenyl)- and 2-(2-hydroxyphenyl)-1H-imidazole toward aliphatic and aromatic isocyanates was studied. Eight ureas were prepared using equivalent mixture of 2-(2-aminophenyl)-1H-imidazole and isocyanate (Et, Pr, isoPr, terc-Bu, Cy, Ph, 4-CH3C6H4, 4-CNC6H4). Similar attempts to obtain related carbamates from 2-(2-hydroxyphenyl)-1H-imidazole lead only to three substituted phenyl carbamates (substituents are 4-CH3, 4-NO2, and 4-CN). In both cases, no reactivity to imidazole ring was observed again.

Heterogeneous CeO2-catalyzed selective synthesis of cyclic carbamates from CO2 and aminoalcohols in acetonitrile solvent

Highly selective synthesis of 2-oxazolidinone from CO2 and 2-aminoethanol in acetonitrile solvent was achieved over heterogeneous CeO2 catalyst. Yield of 2-oxazolidinone reached 97% at 97% 2-aminoethanol conversion with >99% 2-aminoethanol-based selectivity in the optimized reaction conditions. Various aminoalcohols were converted to the corresponding cyclic carbamates in high yields (82% to >99%) with high selectivity (91% to >99%). Complete retention of configuration for the aminoalcohols having a chiral center at the α-position of the hydroxyl group was also achieved. Kinetics and FTIR studies suggested the reaction mechanism over CeO2 that was composed of four steps: (1) formation of carbonate and carbamate adspecies of 2-aminoethanol on CeO2 from 2-aminoalcohol and CO2, (2) decomposition of the carbonate adspecies to the hydroxyl group and CO2, (3) nucleophilic addition of the hydroxyl group to the carbamate adspecies on CeO2, providing 2-oxazolidinone, and (4) desorption of 2-oxazolidinone and regeneration of CeO2.

ChemInform Abstract: N‐Methylimidazole‐Catalyzed Synthesis of Carbamates from Hydroxamic Acids via the Lossen Rearrangement.

An efficient, one-pot, N-methylimidazole (NMI) accelerated synthesis of aromatic and aliphatic carbamates via the Lossen rearrangement is reported. NMI is a catalyst for the conversion of isocyanate intermediates to the carbamates. Moreover, the utility of arylsulfonyl chloride in combination with NMI minimizes the formation of often-observed hydroxamate-isocyanate dimers during the sequence. Under the present conditions, lowering of temperatures is also possible, enabling a mild protocol.

Palladium-Catalyzed Synthesis of N-Aryl Carbamates

Palladium-Catalyzed Synthesis of N-Aryl Carbamates