Acetals cyanation

The monoarylurea may be prepared directly from the amine by heating it in aqueous solution with an equivalent quantity of alkali cyanate and excess of acetic acid, for example ... 

Method 2 (from the free amine). Dissolve 9 - 3 g. (9 1 ml.) of aniline in 10 ml. of glacial acetic acid diluted to 100 ml. contained in a 250 ml. beaker or conical flask, and add with stirring or shaking a solution of 6 5 g. of pure sodium cyanate in 50 ml. of warm water. Allow to stand for 30 minutes, then cool in ice, and allow to stand for a further 30 minutes. Filter at the pump, wash with water and dry in the steam oven. The resulting phenylurea is generally colourless and has a m.p. of 148° (i.e., is pure) the yield is 11 g. If the colour or the m.p. of the product is not quite satisfactory, recrj stallise it from boiling water (10 ml. per gram) as in Method 1. 

Some organosilicon compounds undergo transmetallation. The allylic cyanide 461 was prepared by the reaction of an allylic carbonate with trimethylsi-lyl cyanide[298]. The oriho esters and acetals of the o. d-unsaturated carbonyl compounds 462 undergo cyanation with trimefhylsilyl cyanide[95]. 

Apply sample solubon and spray with 10% car- [101] bon disulfide m ethyl acetate Place TLXZ plate m carbon disulfide vapor for 30 mm, then spray with methanol — sulfunc acid (1-1-1) Heat to 100°C for 10 mm and chromatograph the isothio-cyanates so formed... 

Fluproquazone (97) contains a 2-quinazolinone nucleus and is found to be an analgetic agent useful in mild to moderate pain. One of the preparations involves reaetion of 2-isopropylamino-4-methyl-4 -fluoro-benzophenone (96) with potassium cyanate in hot acetic acid [27],... 

For best results the commercial triethylamine (Matheson, b.p. 89-90°) should be purified to remove primary and secondary amines and water, either by distillation from acetic anhydride and then from barium oxide, or by reaction with phenyliso-cyanate.5 2 3 4... 

It has been shown52 that under similar conditions reduction of the nitrile groups in cellulose ethyl cyanate and of those in the copolymer of vinylidene cyanide with vinyl acetate, proceed simultaneously in two directions with the formation of aldehyde and amine groups. g+ g ... 

Arylthallium bis(trifluoroacetate)s (10.70) are versatile synthons for various reactions, e.g., acylations (Larock and Fellows, 1982) and photolytic cyanations (Taylor et al., 1970), as shown in Scheme 10-93. Copper-catalyzed cyanations (Uemura et al., 1972) can be carried out at 115 °C with arylthallium (acetate)(perchlorate) (Scheme 10-94). 

Acetate kinase is phosphorylated by acetyl phosphate and it has been shown that the phosphoenzyme can synthesise ATP from ADP, and acetyl phosphate from acetate. The mode of decomposition of carbamyl phosphate in aqueous solution is pH dependent and can proceed with either the production of ammonia and carbon dioxide (equation 1), or cyanate (equation 2). No cyanate could be detected during the hydrolysis... 

In a related study, Srivastava and Collibee employed polymer-supported triphenyl-phosphine in palladium-catalyzed cyanations [142]. Commercially available resin-bound triphenylphosphine was admixed with palladium(II) acetate in N,N-dimethyl-formamide in order to generate the heterogeneous catalytic system. The mixture was stirred for 2 h under nitrogen atmosphere in a sealed microwave reaction vessel, to achieve complete formation of the active palladium-phosphine complex. The septum was then removed and equimolar amounts of zinc(II) cyanide and the requisite aryl halide were added. After purging with nitrogen and resealing, the vessel was transferred to the microwave reactor and irradiated at 140 °C for 30-50 min... 

Early studies on 4(5)-aminoimidazole (25 R=H) gave a stable urea derivative (37BJ488). Thus, treatment of a solution of 4(5)-aminoimidazole (25 R = H), made slightly acidic by addition of acetic acid, with potassium cyanate gave AMmidazol-4-yl-urea (31) (8%). TV-Imidazol-4-yl-urea (31) was similarly obtained using the dihydrochloride salt of 4(5)-aminoimidazole (25 R = H) (41MI1). 

Addition of Ketene Acetals and Enoles In recent years, much attention has been given to the synthesis of optically active nitrogen-containing compounds, with the key step being the highly stereoselective nucleophilic addition of ketene silyl acetals to nitrones (Scheme 2.174). Similar to nitrone cyanations, in ketene silyl acetal reactions one observes an accelerating effect with thiourea derivatives (633). 

Dipolar cycloaddition reactions, of nitrones to olefins, 46, 97 of 3-phenylsydnone, 46, 98 Dispiro[5.1.5.1]tetradecane-7,14-dione, photolysis to cyclohexylidene-cyclohexane, 47, 34 preparation from cyclohexanecarbonyl chloride and triethylamine, 47, 34 Displacement of bromine from 1-bromo-2-fluoroheptane to give 2-fluoro-heptyl acetate, 46, 37 N,N -Disubstituted formamidines from triethyl orthoformate and primary amines, 46, 41 N,N-Disubstituted thioureas from secondary amines and silicon tetra-isothiocyanate, 45, 69 N,N-Disubstituted ureas from secondary amines and silicon tetraiso-cyanate, 45, 69... 

The thus prepared /l-trifluoromethylated 0,S-acetal 4 allows us to make a carbon-carbon bond via a carbocation at the -position to the CF 3 group as shown in Scheme 6.9 [48]. Interestingly, Lewis acid-mediated allylation and cyanation can be achieved efficiently only when electrogenerated acids (EGA) are employed. 

CHLOROCYCLOBUTANE, 51, 106 Mesitylene, cyanation, 50, 54 METHALATION OF 2-METHYLPYRIDINE DERIVATIVES ETHYL 6-METHYL-PYRIDINE-2-ACETATE, 52, 75 Metalation, directed, 53, 59 Methallyl alcohol, with phenyl-mercuric acetate to yield 2-methyl-3-phenylpropional-dehyde, 51, 17 METHALLYLBENZENE, 52, 115 7r-Methallylnickel bromide, 52, 115... 

Another reaction type for which EGA catalysis has been thoroughly explored is the reaction between organo-silicon nucleophiles and acetals or unprotected aldehydes and ketones [31-33]. The reaction types are aldol condensation, allyla-tion, cyanation, and hydride reductions depending on which of the nucleophiles (16) to (20) is used. 

Optically active cyanohydrins are obtained in good selectivity by the nucleophilic attack of cyanating reagents to chiral acetals.(21) However, the chiral auxiliaries are destroyed, and not recovered. In catalytic processes with chiral boryl compounds,(22) D-oxynitrilase,(23) and synthetic peptides,(24) the optical purities of the resulting cyanohydrins are generally not sufficient. 

A striking feature of the halide systems of Cd2+ emd Zn2+ is the sudden increase of both AS and AH that takes place at a particular step in complex formation, for = 3 in the case of Cd f- and for = 2 in the case of Zn2+. As already mentioned, a similar though less marked reversal is also observed in the Zn2+ acetate system (Table 1). Among the pseudohalides hsted in Table 2, the same phenomenon occurs in the seleno-cyanate systems of both Zn2+ and Cd2+, but remarkably enough not for the closely analogous thiocyanate systems. The cyanide systems show no sign of such behavior. 

---