Organic carbamate

Organic carbamates (RNHCOO-) commonly display monodentate coordination, as exemplified in the structurally characterized tetrahedral Co(bmc)2Cl2,438 (bmc = lV-(benzimidazoyl-2-yl)-O-methylcarbamate). An unusual route to a carbamato complex involves the reaction of Co2(CO)8 in the presence of a fourfold excess of the stable radical species tmpo, which yields the blue Co40(OOCNC9H18)6 cluster, presumably via a Co(CO)2(tmpo) intermediate, with the nitroxyl radical serving as oxidant.439... 

All of these compounds, whether alkylammonium, metal and p-block carbamates, are potential carriers or sources of carbamic groups, and can be used in the synthesis of organic carbamates [6] if the transfer of the RR NC02 moiety to a suitable organic substrate is accomplished [6, 7]. Moreover, alkylammonium, metal and p-block carbamates, as well as carbamic acid esters, are also potential... 

Yoshida et al. were the first to report the synthesis of carbamate esters by the direct reaction of aliphatic amines, C02 and alkyl halides [47]. The process involved the O-alkylation of intermediate alkylammonium carbamate salt, and required relatively, severe conditions (333-393 K 4MPa C02), long reaction times (1-2 days) and an excess of amine (2.5 equiv.) with respect to the alkylating agent. The method was shown to be effective only with secondary aliphatic amines which, however, were converted into organic carbamates in low to moderate yield and with modest selectivity because of significant side-formation of N-alkylation products. 

Scheme 6.4 Synthesis of organic carbamates from phosphocarbamates.

Recently, organic carbamates have been synthesized by the reaction of amines and alkyl halides with scC02 in the presence of potassium carbonate and an onium salt (Bu4N)Br [52]. In order to ascertain the carbonyl-active species (carbonate or C02 ), the reaction was carried out also with potassium phosphate instead of the carbonate salt the similar results obtained confirmed that scC02 acted in the process not only as a solvent but also as a carboxylating agent. 

Keywords Carbon dioxide Polyethylene glycol C02 transformation Cyclic carbonates Dimethylcarbonate Oxazolidinones Organic carbamates Urea derivatives... 

As an abundant, nontoxic, non-flammable, easily available, and renewable carbon resource, C02 is very attractive as an environmentally friendly feedstock for making commodity chemicals, fuels, and materials [1-7]. In this respect, PEGs-functionalized catalysts have been developed for efficient transformation of C02 into value-added chemicals or fuels such as cyclic carbonates, dimethyl carbonate (DMC), oxazolidinones, organic carbamates and urea derivatives. 

Scheme 5.12 PEG-enhanced synthesis of organic carbamates from amines, C02 and alkyl halides [50]...

An efficient and environmentally benign method for the PEG400-enhanced synthesis of organic carbamates with high chemoselectivity from amines, CO2 and alkyl halides under room temperature and atmospheric pressure utilizing K2CO3 as a base is reported (Scheme 5.12) [50]. PEG probably could serve as both a solvent and PTC, and also activate the carbamic anion so that PEG could depress the alkylation and enhance the selectivity toward the target product. 

Organophosphorus pesticides are anticholinesterases poisoning and its management are described on page 437. Organic carbamates are similar. 

Building block for organic carbamates-isocyanates-carbonates, supplanting... 

Perspectives on the synthesis of organic carbamates (including cyclic carbamates) 12T15. 

Casadei MA, Moracci FM, Zappia G, Inesi A, Rossi L (1997) Electrogenerated superoxide-activated carbon dioxide. A new mild and safe approach to organic carbamates. J Org Chem 62 6754-6759... 

Reviews on synthetic strategies that replace phosgene with CO2 and the use of the latter as a building block for organic carbamates, carbonates, and isocyarmtes have appeared [288, 289]. 

Carafa M, Quaranta E (2009) Synthesis of organic carbamates without using phosgene carbonylation of amines with carbonic acid diesters. Mini-Rev Org Chem 6 168-183... 

Tai-The W, Huang J, Arrington ND, Dill GM (1987) Synthesis and herbicidal activity of. alpha.-heterocyclic carbinol carbamates. J Agric Food Chem 35(5) 817-823 Chaturvedi D, Mishra N, Mishra V (2007) Various approaches for the synthesis of organic carbamates. Curr Org Synth 4 308-320... 

Organic carbamate are stable class of compounds with unique applications in pharmaceutics, agriculture, polyurethane synthesis and more generally. 

SCHEME 5.8 Organic carbamates from a primary amine, aUcyl halide and CO. ... 

Honda, M. Sonehara, S. Yasuda, H. Nakagawa, Y Tomishige, K. Heterogeneous CeOj Catalyst for the One-Pot Synthesis of Organic Carbamates from Amines, CO and Alcohols. Green Chem. 2011,13, 3406-3413. 

Imidazolonium cations allowed the synthesis of organic carbamates. For this, the activation of carbon dioxide has been conducted in O2/CO2 saturated ionic liquids, via electrochemically generated 02. The electron uptake occurred at a less negative potential than the one needed for the direct cathodic reduction of CO2. This kind of electrochemical activation has been applied to the C-N bond formation from amines and CO2 to yield organic carbamates [63]. 

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