Ammonium salts cyanate

Mono-substituted and unsymmetrical di-substituted ureas may be prepared by a modification of Wohler s urea synthesis, salts of primary or secondary amines being used instead of the ammonium salt for interaction with potassium cyanate. Thus when an aqueous solution containing both aniline hydrochloride and potassium cyanate is heated, aniline cyanate is first formed, and then C,HjNH,HCl -h KCNO = C,H6NHj,HCNO -h KCl C,HsNH HCNO = C.H NHCONH, by the usual molecular rearrangement is converted into monophenyburea. 

The nitrogen of aHphatic and aromatic amines is alkylated rapidly by alkyl sulfates yielding the usual mixtures. Most tertiary amines and nitrogen heterocycles are converted to quaternary ammonium salts, unless the nitrogen is of very low basicity, eg, ia tn phenylamine. The position of dimethyl sulfate-produced methylation of several heterocycles with more than one heteroatom has been examined (22). Acyl cyanamides can be methylated (23). Metal cyanates are converted to methyl isocyanate or ethyl isocyanate ia high yields by heating the mixtures (24,25). 

Ammonium cyanate, urea from, 2 Ammonium ion, acidity of, 921-922 Ammonium salt, IR spectroscopy of. 952-953... 

Solutions of cyanates give with AgN03, white precipitate—AgCNO, soluble in ammonia decomposed by acids with liberation of C02 and formation of an ammonium salt. 

The analysis of cyanate is based on its total conversion to an ammonium salt. This is achieved by heating the acidified sample. The reaction is shown below ... 

The combination of Me2AlCN and BINOL (1.2 equiv.) also induced the cyanation of imines derived from benzaldehyde, affording the Strecker products in up to 70% ee [76]. Finally, N-allylbenzaldimines have been reported to react with HCN in the presence of chiral ammonium salt catalysts [77, 78]. 

Ammonium Cyanate.— The corresponding ammonium salt, viz., ammonium cyanate, NH4OCN, may be easily prepared from the potassium cyanate by treating a solution of the latter with the calculated amount of ammonium sulphate. This compound is of especial interest because on evaporation of the water solution to dryness a rearrangement takes place and urea is formed (p. 429). Ammonium cyanate is also formed when iso-cyanic acid is neutralized with ammonia. 

With ferric salts in solution either of these reagents forms the cherry red ferric thio-cyanate and is the basis of qualitative tests for iron and the use of the thio-cyanate as an indicator in volumetric titrations. Potassium thio-cyanate may be prepared by heating potassium cyanide with sulphur or ammonium sulphide. Ammonium thio-cyanate may be prepared by heating together carbon disulphide and ammonia in the presence of alcohol. 

Some other very important events in the historic development of asymmetric organocatalysis appeared between 1980 and the late 1990s, such as the development of the enantioselective alkylation of enolates using cinchona-alkaloid-based quaternary ammonium salts under phase-transfer conditions or the use of chiral Bronsted acids by Inoue or Jacobsen for the asymmetric hydro-cyanation of aldehydes and imines respectively. These initial reports acted as the launching point for a very rich chemistry that was extensively developed in the following years, such as the enantioselective catalysis by H-bonding activation or the asymmetric phase-transfer catalysis. The same would apply to the development of enantioselective versions of the Morita-Baylis-Hillman reaction,to the use of polyamino acids for the epoxidation of enones, also known as the Julia epoxidation or to the chemistry by Denmark in the phosphor-amide-catalyzed aldol reaction. ... 

I. V. P. Raj, G. Suryavanshi, A. Sudalai, Tetrahedron Lett. 2007, 48, 7211—7214. Organocatalytic activation of TMSCN by basic ammonium salts for efficient cyanation of aldehydes and imines. 

Asymmetric phase-transfer catalytic addition of cyanide to C=N, C=0, and C=C bonds has been recently explored, which has been demonstrated to be an efficient method toward the synthesis of a series of substituted chiral nitriles. In this context, Maraoka and coworkers disclosed an enantioselective Strecker reaction of aldimines by using aqueous KCN [140]. In this system, the chiral quaternary ammonium salts (R)-36e bearing a tetranaphthyl backbone were found to be remarkably efficient catalysts (Scheme 12.25). Subsequently, this phase-transfer-catalyzed asymmetric Strecker reaction was further elaborated by use of a-amidosulfones as precursor of N-arylsulfonyl imines. Interestingly, the reaction could be conducted with a slight excess of potassium cyanide [141] or acetone cyanohydrin [40] as cyanide source, and good to high enantioselectivities were observed. In contrast, the asymmetric phase-transfer-catalytic cyanation of aldehydes led to the cyanation products with only moderate enantioselectivity [142]. 

Little more than a decade later, the vitalistic theory suffered still further when Friedrich Wohler discovered in 1828 that it was possible to convert the "inorganic" salt ammonium cyanate into the "organic" substance urea, which had previously been found in human urine. 

Salts of semicarbazide have been prepared by the action of potassium cyanate on hydrazine sulfate 1 by the action of hydrazine hydrate on urea 2 by heating hydrazine ammonium carbonate 3 bv the reduction of nitrourea with zinc dust and hydrover. 27, 31 (1894). 

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