Azides transformation

The Conversion of Hydrazines to Azides Hydrazine-azide transformation... 

Formation of Reactive Intermediates. It is possible under the right conditions to prepare lead azide in four different forms. There is, however, not much difference in their sensitivities [121], suggesting that spontaneous initiation is not due to polymorphism. Under certain conditions j3-lead azide transforms to a-lead azide, but the difference in enthalpy of formation is so small that any energy released in the j3-to-a transformation is unlikely to initiate explosion [126]. 

Tertiary alcohols are converted directly to azides using NaN3/ Sulfuric Acid or HN3/Boro Trifluoride or TUanium(IV) Chloride (eq 5), and the carboxylic acid to acyl azide transformation (often en route to Curtius rearrangements to isocyanates) occurs with DPPA or via activation with DMF/Thionyl Chloride. ... 

Curtius transformation An alternative to the Hofmann transformation for obtaining an amine from an ester via the hydrazide, azide and isocyanate. Thus ethyl ethanoate is converted into melhylamine by the following series of reactions ... 

A potential advantage of the Schmidt reaction is illustrated by the conversion of progesterone to the 17j5-acetylamino derivative, without affecting the A-ring. A 35 % yield is obtained when 1 mole of sodium azide in polyphos-phoric acid is used. With excess azide the A-ring is transformed into an a,jS-unsaturated lactam ... 

To reduce the danger of an explosion in this reaction, trifluoromethanesuifonyi azide can be generated in methylene chloride in situ and used for subsequent transformations without isolation [775]... 

Sodium azide does not react with carbonyl sulfide to form 5-hydroxy-1,2,3,4-thiatriazole, nor with carboxymethyl xanthates, RO-CS SCH2COOH, to form 5-alkoxy-l,2,3,4-thiatriazoles. The latter, however, could be prepared from xanthogenhydrazides (RO-CS NHNH2) and nitrous acid. They are very unstable and may decompose explosively at room temperature only the ethoxy compound (6) has been examined in detail. This is a solid which decomposes rapidly at room temperature and even at 0°C is transformed after some months into a mixture of sulfur and triethyl isocyanurate. In ethereal solution at 20° C the decomposition takes place according to Eq. (16)... 

Interest in the mechanism and product distribution of thermal and photochemical transformations of aryl azides led to the isolation of some nitrogen-containing derivatives of heptafulvalene. Based on elemental analysis and spectroscopic data it has been suggested tentatively that the compound isolated following vapor-phase pyrolysis of azidopentafluoro-... 

Reductive alkylations have been carried out successfully with compounds that are not carbonyls or amines, but which are transformed during the hydrogenation to suitable functions. Azides, azo, hydrazo, nitro and nitroso compounds, oximes, pyridines, and hydroxylamines serve as amines phenols, acetals, ketals, or hydrazones serve as carbonyls 6,7,8,9,12,17,24,41,42,58). Alkylations using masked functions have been successful at times when use of unmasked functions have failed (2). In a synthesis leading to methoxatin, a key... 

Intermediate 37 can be transformed into ( )-thienamycin [( )-1)] through a sequence of reactions nearly identical to that presented in Scheme 3 (see 22— 1). Thus, exposure of /(-keto ester 37 to tosyl azide and triethylamine results in the facile formation of pure, crystalline diazo keto ester 4 in 65 % yield from 36 (see Scheme 5). Rhodium(n) acetate catalyzed decomposition of 4, followed by intramolecular insertion of the resultant carbene 3 into the proximal N-H bond, affords [3.2.0] bicyclic keto ester 2. Without purification, 2 is converted into enol phosphate 42 and thence into vinyl sulfide 23 (76% yield from 4).18 Finally, catalytic hydrogenation of 23 proceeds smoothly (90%) to afford ( )-thienamycin... 

Azide is widely useful as a surrogate for ammonia in nucleophilic substitution reactions, due to its high nucleophilicity, low basicity, and stability towards a variety of conditions for subsequent transformations. In particular, the azidolysis of... 

Recendy, Guiver et al. reported a number of derivatives of polysulfone and poly(aryl sulfone).172 188 Polysulfones were activated either on the ortho-sulfone sites or the ortho-ether sites by direct lithiation or bromination-lithiation. The lithiated intermediates were claimed to be quantitatively converted to azides by treatment with tosyl azides. Azides are thermally and photochemically labile groups capable of being transformed readily into a number of other useful derivatives. 

Chalcone dibromides are advantageous intermediates for the preparation of various nitrogen-containing heterocycles (refs. 1-4). In the case of exocyclic a,P-unsaturated ketones, however, only few examples are known concerning the utilization of their dibromides for such purposes (ref. 5). Our aim was, therefore, the synthesis of the dibromides of various exocyclic a,P-unsaturated ketones (ref. 6) and to study their chemical transformations. In our present paper the reaction of such dibromides with azide nucleophile is reported. 

Ben2yl azide 1855 and N-benzyloxycarbonylbenzylamine 1859 are both transformed by the cheap polymethylhydrosiloxane (PMHS) 1856, in the presence of (B0C)20 and Pd/C, into 92-94% N-BOC-benzylamine 1857 and the polymer 1858 [81]. (Scheme 12.22). Aromatic and aliphatic amine oxides are readily reduced by 1856/Pd/C into their corresponding amines. Thus, e.g., pyridine-N-oxide 860 and quinohne-N-oxide 877 give pyridine and quinohne in 90 and 92% yield, respectively. Analogously, benzyldimethylamine-N-oxide is converted in 88% yield into free benzyldimethylamine [82]. 

Reaction of 47 with NBS in carbon tetrachloride afforded the tribromide (240, 100%). After replacement of the primary bromo group with benzoyl-oxyl, the product (241,47%) was debrominated with zinc dust in ethanol to give the diene (242,64%). Epoxidation of242 produced the isomeric compounds 243 and 244, which were transformed into the azides (245 and 246), convertible into valienamine isomers. ... 

Another examination involves a synthesis of thienobenzazepines based on the formation of key intermediate 6 prepared according to the method of McDowell and Wisowaty (Scheme 6.2). ° Selective reduction of this intermediate using zinc dust in 28-30% ammonia solution afforded the benzoic acid 7, which upon subsequent Curtius rearrangement and aluminum trichloride-mediated cyclization furnished the oxo-azepine 8. While this synthetic approach gave the tricycle in a few synthetic transformations, many of the same concerns as above exist when considering large scale preparation of 8 the use of large amounts of zinc, sodium azide, and aluminum trichloride. 

The transformation can also be carried out on the acid using diphenylphosphoryl azide (DPPA).266... 

Sodium hydrogen telluride, (NaTeH), prepared in situ from the reaction of tellurium powder with an aqueous ethanol solution of sodium borohydride, is an effective reducing reagent for many functionalities, such as azide, sulfoxide, disulfide, activated C=C bonds, nitroxide, and so forth. Water is a convenient solvent for these transformations.28 A variety of functional groups including aldehydes, ketones, olefins, nitroxides, and azides are also reduced by sodium hypophosphite buffer solution.29... 

An azide group can be transformed into a thiocyanate group by reduction with LiAlH4 followed by treatment with NJSl -thiocarbonyldiimidazole.[ 14]... 

A way to introduce the primary amino group directly onto the selenophene ring is via the azido compound, obtained by nucleophilic substitution of the bromo derivative with sodium azide. Useful transformations of the azido group are shown in Scheme 12.117 The amino aldehyde (109) is a suitable starting material for the preparation of selenolo[3,2-b]pyridine (110) by the Friedlander reaction.138 Not only can the azido be reduced to an amino... 

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