Sodium azide anhydrides

Another nittogen-containing inflate derivative, trifluoromethanesuifonyi azide, IS prepared by the reaction of triflic anhydride with aqueous sodium azide [775] and IS used as an efficient reagent for the synthesis of alkylazides from alkylanunes (equation 58)... 

Treatment of N-benzoyl-L-alanine with oxalyl chloride, followed by methanolic triethylamine, yields methyl 4-methyl-2-phenyloxazole-5-carboxylate 32 <95CC2335>. a-Keto imidoyl chlorides, obtained from acyl chlorides and ethyl isocyanoacetate, cyclise to 5-ethoxyoxazoles by the action of triethylamine (e.g.. Scheme 8) <96SC1149>. The azetidinone 33 is converted into the oxazole 34 when heated with sodium azide and titanium chloride in acetonitrile <95JHC1409>. Another unusual reaction is the cyclisation of compound 35 to the oxazole 36 on sequential treatment with trifluoroacetic anhydride and methanol <95JFC(75)221>. 

The aziridine aldehyde 56 undergoes a facile Baylis-Hillman reaction with methyl or ethyl acrylate, acrylonitrile, methyl vinyl ketone, and vinyl sulfone [60]. The adducts 57 were obtained as mixtures of syn- and anfz-diastereomers. The synthetic utility of the Baylis-Hillman adducts was also investigated. With acetic anhydride in pyridine an SN2 -type substitution of the initially formed allylic acetate by an acetoxy group takes place to give product 58. Nucleophilic reactions of this product with, e. g., morpholine, thiol/Et3N, or sodium azide in DMSO resulted in an apparent displacement of the acetoxy group. Tentatively, this result may be explained by invoking the initial formation of an ionic intermediate 59, which is then followed by the reaction with the nucleophile as shown in Scheme 43. 

The acyl azide intermediates are prepared either by reaction of sodium azide with a reactive acylating agent or by diazotization of an acyl hydrazide. An especially convenient version of the former process is treatment of the carboxylic acid with ethyl chloroformate to form a mixed anhydride, which then reacts with azide ion.265... 

Sodium, with l-bromo-3-chloro-cyclobutane to give bicyclo [l.l.O]butane, 51, 55 Sodium amalgam, 50, 50, 51 Sodium amide, with 2,4-pentane-dione and diphenyliodonium chloride to give l-phenyl-2, 4-pentanedione, 51, 128 Sodium azide, 50, 107 with mixed carboxylic-carbonic anhydrides, 51, 49 Sodium borohydride, reduction of erythro-3-methanesulfony-loxy-2-butyl cyclobutanecar-boxylate, 51, 12 reduction of 2-(1-phenylcyclo-pentyl)-4,4,6-trimethyl-5,6-dihydro-1,3(4H)-oxazine to 2-(1-phenylcyclopentyl)-4,4, 6-trimethyltetrahydro-l,3-oxazine, 51, 25 Sodium cyanoborohydride, used... 

The usual procedure of preparing acid azides, which involves treating an acid chloride with sodium azide,8,9 suffers from the disadvantage that it is often difficult to obtain pure acid chlorides in good yields from acids which either decompose or undergo isomerization in the presence of mineral acids.7 Synthesis of the azide by way of the ester and hydrazide10 has been used to circumvent this difficulty but is much less convenient. The present procedure permits ready formation of acid azides in excellent yields from mixed carboxylic-carbonic anhydrides and sodium azide under very mild conditions. 

Acetic anhydride. Nitric acid, Hexamine, Acetic acid. Methylene chloride, Sodiiun bicarbonate. Magnesium sulfate, Dioxane, Hydrogen chloride. Acetone, Sodium azide... 

Aluminum powder, Carbon tetrachloride Aluminum powder, Tetrachlorethylene CNTA, Hydrogen sulfide. Benzene, Lead 11 hydroxide Mercury-ll-nitrate, Sodium azide Mercury, Nitric acid. Alcohol Mercury, Nitric acid. Ethanol Ammonia, Mercury oxide. Nitric acid Nitric acid. Methylene diformamide. Acetic anhydride. Formic acid. Benzene... 

Benzene, Arsenic trichloride, Aluminum chloride. Hexanes Acetic anhydride. Nitric acid, Hexamine, Acetic acid, Methylene chloride. Sodium bicarbonate, Magnesium sulfate, Dioxane, Hydrogen chloride, Acetone, Sodium azide m-phenylenediamine, Methanol, Sodium carbonate, Ethyl chloromate, Ethylene glycol dimethyl ether, Sulfuric acid, Nitric acid... 

A stirred mixture of methyl 2,3-di-0-acetyl-4,6-dichloro-4,6-dideoxy-a-D-galactopyrano-side (41, 1 mmol) [prepared by acetylation (acetic anhydride-pyridine) of methyl 4,6-dichloro-4,6-dideoxy-a-D-galactopyranoside 37], sodium azide (4 mmol), and dry N,N-... 

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. 

An analogous result was first observed by Thomas <1993S767> and has also been reported elsewhere <2000JME488>. However, in the latter study, the secondary amide was converted into a tetrazole using trifluoro-methanesulfonic anhydride (Tf20) and sodium azide. 

Shikimic acid Sodium azide Dimethoxypropane Triethylamine Trityl chloride Triphenylphosphine Acetic anhydride Ethanol... 

Several different nucleophilic displacement reactions of ring substituents were utilized in the synthesis of 3-azido-oxetane-2-carboxylates (Scheme 12) <2001TL4247>. The triflate ester 66, prepared from the corresponding trans-/3-hydroxy ester and triflic anhydride, was displaced by reaction with sodium azide, and inversion of configuration, to... 

Pyridopyrimidine systems may also be accessed by in situ generation of pyridylisocyanates <2003TL2745>. Treatment of 2,3-pyridinccarboxylic anhydride with methanol leads to the formation of 2-(methoxycarbonyl)nicotinic acid that undergoes Curtius rearrangement on conversion to the 3-acyl azide with sodium azide and ethyl chloro-formate. Condensation of the resulting isocyanate with a series of amino acids leads to the synthesis of pyrido[3,2- T pyrimidines in good to excellent yield (Scheme 19). 

The reaction of compound (86) with hydroxylammonium chloride in acetic anhydride in the presence of pyridine gave the corresponding cyano-substituted compound (252). Alkaline hydrolysis of compound (252) gave the diacid (253), and reaction with sodium azide and ammonium chloride in DMF led to the tetrazole (254). The compounds (8i), (82), (84), (85), and (87) reacted similarly <93CCC2139, 94MI 701-01). 

Reaction of the benzodioxocine 170 with the epoxidation reagent resulted in the epoxide 171, which was then opened with sodium azide in situ to provide trans-racemic azide 172 (Scheme 18) <2004MI265>. Reduction of the azide 172 by hydrogenolysis using Pd on carbon gave trans-racemic amine 173 in 70% yield over three steps. On acylation of the amine with acetic anhydride, the trans-racemic alcohol 174 was formed, which was then oxidized with Dess-Martin periodinane into the unstable dioxocinone 175. 

Hazards Wear gloves and use maximum ventilation when handling 99% nitric acid. Avoid inhalation of the fumes. Extinguish all flames before using acetic anhydride, acetone, or dioxane, and avoid inhalation of the vapors. Use care when handling sodium azide, and avoid skin contact or ingestion. Sodium azide is very toxic. Note Dioxane is a suspected carcinogen... 

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