Cyanate, carbamoylation

Another addition reaction of amino groups is carbamoylation with sodium cyanate (Eq. 3-35). A displacement reaction by an amino group on an acid... 

E. (S)-(-l-l-Carbamoyl-Z-methoxymethylpyvrolidine. The aqueous amine hydrochloride solution is adjusted to a pH of 2.8-3.2 (Note 13) with aqueous 50% potassium hydroxide. A solution of 80 g (1 mol) of potassium cyanate (Note 14) in 140 mL of water is then added all at once at 15°C and the mixture is allowed to stir for at least 12 hr at 20°C. 

The classical Kolbe-Schmidt reaction treats alkali metal phenoxides and carbon dioxide at higher than atmospheric pressure, giving salicylic acid. Hirao and Kato developed several modifications for industrial production ". Recently, phenol phosphate was enzymatically carboxylated, giving p-hydroxybenzoic acid ". As for related reactions, Sartori and coworkers conducted o-carbamoylation of aluminum or boron phenoxides with alkyl isocyanate ", and Adachi and Sugasawa o-cyanated phenols using methyl thioisocyanate in the presence of BCI3 (equation 54). ... 

C5. Cocco, D., Rossi, L., Barra, D., Bossa, F., and Rotilio, G., Carbamoylation ofCu,Zn-superoxide dismutase by cyanate. Role of lysines in the enzyme action. FEBS Lett. 150,303-306 (1982). 

Lewis acid-catalyzed condensation of an aryl carbonitrile (2 equivs.) with an acyl halide (1 equiv.) is a well-established and popular route to 1,3,5-oxadiazinium salts (see Section 6.18.10.3.l.i). The carbonitrile can be replaced successfully by aryl cyanates, cyanamides, and alkylthiocyanates, and examples using carbamoyl chlorides rather than the acyl halide have also been reported. The 1,3,5-oxadiazinium salts are also accessible by cyclocondensation of A-acylchloroformamidines with cyanamides in the presence of stannic chloride (see Section 6.18.10.2.2.l.i) and by condensation of A A -disubstituted-ALacylthioureas (2 equivs.) with thionyl chloride or phosphorus pentachloride (see Section 6.18.10.2.2.i). 

Various alkyl isothiocyanates formed on enzymatic hydrolysis of non-indolyl glucosinolates of rapeseed were determined by GC-MS d70 Carbamoyl isothiocyanates (24) in solution exist in equilibrium with thiocarbamoyl cyanates (25). This equilibrium is well established at 80-90 °C. The species have distinct absorption bands in the IR region at 1980 and 2240 cm for 24 and 25, respectively ... 

The thiazolium chlorides (146) are convertible into the mesionic phenyl-(thio)carbamoyl derivatives (148) by phenyl iso(thio)cyanate, and into the mesionic 5-benzenesulphonyliminothiazole (149) by benzenesulphonyl chloride in alkaline media (Scheme 8). Detailed spectral data for each of the new types of compound were provided. ... 

Carbamoylation with cyanate attacks a- and 8-amino groups as well as cysteine and tyrosine residues. However, their derivatization is reversible under alkaline conditions ... 

Ethyl carbamate in wine is formed (mostly at the end of fermentation) from urea. The intermediates of its degradation are probably cyanates and cyanic acid (HO-C=N), also known as hydrogen cyanate, which may isomerise to isocyanic acid (H-N=C=0). Iso-cyanic acid can also arise by protonation of the cyanate anion and nucleophilic addition of ethanol to isocyanic acid yields ethyl carbamate. Isocyanic acid also reacts with other nucleophilic reagents, such as water (with formation of ammonia and carbon dioxide), thiols and amino groups of proteins. By catalysis with ornithinecar-bamoyl transferase, citrulline is transformed into ornithine and carbamoyl phosphate, the ethanolysis of which yields ethyl carbamate (Figure 12.39). 

Potassium [ C]cyanate is most easily prepared by oxidation of K CN with KMn04 . Addition of ammonia and amines to K CNO is its main application in carbon-14 synthesis. The ammonolysis of K CNO upon heating with aqueous ammonia is one of the standard procedures for preparing [ C]urea . Upon its reaction with primary or secondary amines, unsymmetrical [ CJureas such as iV-[ C]carbamoyl aspartic acid 108 are obtained (Figure 7.29). Reaction of two equivalents of K CNO with hydrazine produced... 

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