Nitrite with isocyanates

Incompatible with sulfuric acid, isocyanates, chlorates, nitrates, nitrites, with loss of toxic ammonia, hydrogen sulfide, and sulfur trioxide gases. In temperatures above 302°F/150°C, releases toxic flunes of ammonia, hydrogen sulfide, and oxides of nitrogen and sulfiir. 

Several approaches to the 1,2,3-triazole core have been published in 2000. Iodobenzene diacetate-mediated oxidation of hydrazones 152 led to fused 1,2,3-triazoloheterocycles 153 <00SC417>. Treatment of oxazolone 154 with iso-pentyl nitrite in the presence of acetic acid gave 1,2,3-triazole 155, a precursor to 3-(W-l,2,3-triazolyl)-substituted a,P-unsaturated a amino acid derivatives <00SC2863>. Aroyl-substituted ketene aminals 156 reacted with aryl azides to provide polysubstituted 1,23-triazoles 157 <00HC387>. 2-Aryl-2T/,4/f-imidazo[43-d][l,2,3]triazoles 159 were prepared from the reaction of triethyl AM-ethyl-2-methyl-4-nitro-l//-imidazol-5-yl phosphoramidate (158) with aryl isocyanates <00TL9889>. 

Further variations for the synthesis of this ring system has been published by M. F. G. Stevens et al. (Scheme 12). Thus, the methyl-substituted cyclic carbamate 37 when treated with sodium nitrite in aqueous tartaric acid yielded temozolomide 9a in average yield (45%) <1997JOC7288>. Two other approaches also proved to be applicable to the synthesis of a great number of derivatives the diazoimidazole carboxamide 32 was reacted with various isocyanates to... 

Goodman and Chorev 75 found that the required a-aminoacyl azides 14 are best prepared by reaction of the mixed anhydride of the amino acid with sodium azide. This method led to slightly better yields than the nitrosylation of TV-formylaminoacyl hydrazide. Curtius rearrangement of the a-aminoacyl azide 14 yielded the isocyanate 16, which was subsequently trapped as 17 or 18 as shown in Scheme 2. Comparable yields were obtained by nitrosylation with tert-butyl nitrite. 76 Other methods of acyl azide formation have rarely been employed for PMRI-peptide synthesis. Only Fincham et al. 11 reported the use of trimethylsilyl azide to synthesize an acyl azide en route to a PMRI-peptide. 

Preparation of tri-1 -naphtyl isocyanurate 3d A mixture of naphthyl isocyanate Id (3.38 g, 20 mmol) and sodium piperidinedithiocarbamate 2 (18.3 mg, 0.1 mmol) or sodium nitrite (55.2 mg, 0.8 mmol) was taken in a Teflon tube with screw cap and was then placed inside the microwave oven and irradiated for 5 min at 385 W. After 5 min (during this period it gently cools to about room temperature) it was irradiated again at the same power for another 5 min. The reaction mixture was allowed to cool to room temperature and the resultant residue washed with 50 mL ether. Trituration of the crude residue with water led to the title compound which was recrystallized from ethanol to give 81% of 3d. 

Method B Phenoxypropionyl hydrazide (125.9 g, 0.7 mol) is suspended in 650 ml ice-water and concentrated hydrochloric acid (123 ml, 1.47 mol) was added. The mixture is stirred for 20 min and toluene (350 ml) is added. A solution of sodium nitrite (53.1 g, 0.77 mol) in 200 ml water is added over a period 15 min. The internal temperature is kept below 15°C and if necessary, ice is directly added to the reaction mixture. After the addition is completed the mixture is stirred for a further 1 hour and filtered through Celite. The solid is washed with 30 ml toluene and the filtrate is separated. The aqueous layer is extracted with 200 ml toluene and the combined toluene solutions are dried over MgS04. The dried toluene solution is filtered and added dropwise to a preheated flask at 95°-100°C. Nitrogen evolution occurs as the solution is dropped in. After the addition is complete, the reaction mixture is heated to gentle reflux until nitrogen evolution has ceased. The reaction mixture is cooled to room temperature and can be used directly in subsequent reactions. 1 ml of the reaction mixture is withdrawn and evaporated to dryness, and the weight of the residue is measured. This provides an estimate of the concentration of isocyanate per ml of reaction mixture. 

As described earlier (Section 4.4.1.1), the intermediates of the Curtius reaction are acyl azides, which themially rearrange to isocyanates. One of the classical procedures for the preparation of acyl azides consists of the formation of hydrazides from esters and hydrazine, followed by treatment of the hydrazides with nitrous acid, generated from sodium nitrite and acetic, hydrochloric or sulfuric acid. Acyl azides are commonly used in the crude state or in solution since they are thermally unstable and potentially explosive. 

Nitrosolysis of camphor ethyl acetal with ethanolic ethyl nitrite in sulphur dioxide yields the orthoester oxime (205) which is rapidly dehydrated by excess acetal to the orthoester nitrile which then reacts with sulphur dioxide to form the ester nitrile and diethyl sulphite.Further papers in this section include the full paper on ozonolysis of silyl ethers (Vol. 5, p. 33), another synthesis of camphor-enol trimethylsilyl ether (cf. Vol. 6, p. 41)/°° the conversion of camphor oxime with Grignard reagents into the corresponding imine with no aziridine formation/° the preparation of (206) by treating bornylene with trichloroacetyl isocyanate/ the oxidation of thiocam-phor to the 5-oxide and alkylation in the presence of thallium(i) ethoxide to a/S-unsaturated sulphoxides/ and the free-radical C-3 alkylation of camphor with alkenes. " ... 

The 3-imino group of 4-cyano-2-ethyl-3-imino-2,3,5,6,7,8-hexahydro-l//-pyrido[l,2-c]pyrimidine-l-thione was acylated with phenyl isocyanate (78MI1). The imino group of l-imino-4-cyano-3-methylthio-l//-pyrido[l,2-cjpyrimidine was alkylated and acylated with methyl iodide and acetic anhydride (75YZ13). Reaction of 3-amino-4-phenyl-4-[2-(A, N-di-n-pro-pylamino)ethyl-4,4 a,5,6,7,8-hexahydro-l //-pyrido[l, 2-c ]pyri midin-l-one with acetic anhydride in pyridine and with sodium nitrite in aqueous acetic acid afforded 3-acetamido and perhydro-l,3-dioxo derivatives, respectively (87USP4680295). 

AMMONIUM SULPHATE (7783-20-2) H8N2O4S Noncombustible solid. Aqueous solution is a strong acid. Violent reaction with fused potassium chlorate potassium nitrite. Reacts with caustics, forming ammonia. Hot material reacts with nitrates, nitrites, chlorates. Incompatible with strong oxidizers sulfuric acid aliphatic amines alkanolamines, amides, organic anhydrides isocyanates, vinyl acetate aUcylene oxides epichlorohydrin. Mixture with sodium hypochlorite forms nitrogen trichloride, an unstable explosive material. Attacks metals in the presence of moisture. 

Combustible solid.Dust may form explosive mixture with air (flash point 334°F/168°C Fire Rating 1). Violent reaction with nitric acid forms explosive nitro materials in the presence of sulfuric acid. Dust and powder forms explosive mixture with air. Incompatible with strong acids, alkalis, aliphatic amines, alkanolamines, alkylene oxides, ammonia, epichlorohydrin, isocyanates, nitrates, nitromethane, sodium nitrite, strong oxidizers. On small fires, use dry chemical powder (such as Purple-K-Powder), Halon , alcohol-resistant foam, water spray, or CO2 extinguishers. Combustion produces phthalic anhydride and carbon oxides. 

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