Azides azidoformates

Metallic Pd is a good catalyst for the conversion of the primary azide 34 into the nitrile 35 in the presence of a hydrogen acceptor such as diphenylacety-lene[33]. By this method, organic halides can be converted into nitriles without increasing the carbon number. Reaction of the azidoformate 36 with an allylic... 

Tests conducted by the Eastman Kodak Company have shown that tert-butyl azidoformate [Formic acid, azido, -butyl ester], also known as iert-butoxy carbonyl azide and 1-BOC azide, is a thermally unstable, shock-sensitive compound (TNT equivalence 45%). 

The photolytic and thermolytic decomposition of azides in the presence of olefins has been applied to aziridine synthesis. However, only a limited number of steroid aziridines have been prepared in this manner. The patent literature reports the use of cyanogen azide at ca. 50° for 24 hours in ethyl acetate for the preparation of an A-nor- and a B-norsteroidal aziridine. The addition is believed to proceed via a triazoline. The reaction of cholest-2-ene with ethyl azidoformate takes place in a nonselective manner to produce a mixture of substances, including C—H insertion products. 

The concentration of alkyl azidoformate used in these decompositions is important since with an excess (0.5 molar equiv) of azide, thermolysis at 130°C results in the formation of 1 2 1 //-azepine (methoxycarbonyl)nitrene adducts as the major products.145,146... 

In the formation of tert-butyl azidoformate by the addition of phosgene to alcohols followed by the addition of Na nitride or hydrazoic acid in the presence of pyridine, reaction of phosgene with the azide can cause the formation of expl carbazide (Ref 9)... 

The triazoles previously obtained from jS-keto-ylides and acyl azides or ethyl azidoformate are the 2-acyltriazoles (80) formed by isomerization under the basic conditions of the initially formed 1-substituted triazoles (79). The latter can be isolated in some cases if the reactions are interrupted. Aryl mono- and bis-azides have also been used in the preparation of the triazolcs (81). 

The reaction of ethyl azidoformate (93) with tetramethylallene yielded triazoline 94 and oxazoline 95 [88]. The triazoline 94 was formed by [3 + 2]-cycloaddition of azide 93 to the allene. The oxazoline 95 may result from [3 + 2]-cycloaddition of car-bethoxynitrene (96), which is formed from 93 by nitrogen evolution, to the allene or by the [2 +1] addition of the nitrene and subsequent rearrangement. 

V - B u ty 1 am i d o s u 1 lu ry 1 azide, 1693 tert-Butyl azidoformate, 1936 Carbonic diazide, 0550 Carboxybenzenesulfonyl azide, 2699 4-Chlorobenzenesulfonyl azide, 2152 4-Chlorobenzoyl azide, 2654 /V-(2-Chloroethyl)-/V-nitrosocarbamoyl azide, 1131 Cyanodiazoacetyl azide, 1346 Cyanohydrazonoacetyl azide, 1083... 

Ethyl azidoformate, 1193 Fluorothiophosphoryl diazide, 4308 2-Furoyl azide, 1821 Glutaryl diazide, 1874... 

Azidoformic esters such as 342 react with Cgg in a [2-tl] addition (Scheme 4.70), if the temperature is high enough to induce the loss of nitrogen prior to addition, otherwise a [3-1-2] addition can be observed (Section 4.3.2) [172, 395, 397]. Typical conditions include heating of the mixture in solvents such as tetrachloroethane [395, 397, 398], chloronaphfhalene [397] or toluene [396] at 110-160 °C. These conditions also afford multiple addition products [172]. To avoid potential hazard during purification of the azido formiates, they were also generated in situ in one pot by the reaction of chloro-formic ester with sodium azide [396]. 

Gallagher and co-workers (11) reported the cycloadditions of electron-dehcient azides with the ketene-(5, 5)-acetals (46) (Scheme 9.11). Reaction of p-toluenesul-fonyl azide with 46 gave the unstable cycloadducts 47, which underwent rearrangement to afford compounds 48 in 24—89% yield. In the case of ethyl azidoformate. 

The stereoselective intermolecular cycloaddition of azides to chiral cyclopenta-none enamines was reported, but both product yields and enantiomeric excesses (ee) were low (24) (Scheme 9.24). Ethyl azidoformate (115) and A-mesyl azido-formamimidate (116) underwent 1,3-dipolar cycloaddition with the monosubsti-tuted chiral enamine 114 to give products 117 and 118 in low yields with ee of 24 and 18%, respectively. Intermolecular cycloaddition of the A-mesyl azidoforma-mhnidate 116 with the disubstituted C2-symmetric chiral enamine 119 proceeded with good diastereoselectivity to give compound 120 in 18% yield. On cleavage of the enamine unit, compound 120 afforded 118 with low ee. 

Azidoformic Acid Methytester (Azidoameisen-saure-methylester, Triazoameisensaure-methylester, Carbazidsaure-methylester or Stickstoffkohleasaure-methylester in Ger), N3.CO.O.CH3 mw 101.06, N 41.58%, OB —55.4% colorless liq, bp 102—3° exploded occasionally when distilled under atm pressure. May be prepd by warming for 1 hr ethereal soln of Am azide with methyl ester of chloroformic acid, Cl.CO.O.CHg. 

Aryl azide, acyl azide, sulfonyl azides, and azidoformate add to olefins by a 1,3-dipolar cycloaddition mechanism to yield triazoline. This addition also occurs with other unsaturated systems such as a,/S-unsaturated olefins, enam-ines, and cynamines [48]. 

Nitrene intermediates are formed in the thermal decomposition reactions of most alkyl azides, aryl azides, sulfonyl azides, and azidoformates. Some decompositions, however, must be regarded as proceeding by a synchronous mechanism. They are discussed in this section. 

Kreher and Jager have studied the aluminum chloride catalyzed decomposition of azidoformates in several solvents.18118 They reasonably assumed that the decomposition process in n-hexane and nitromethane solution proceeds by C02 elimination and the formation of alkyl azides which then decompose into imines (eq 5). Furthermore, infrared analysis has shown that the catalyst is fixed at the carbonyl group of the azido-formate. 

Analogous methyl azidoformate forms with norbornene a thermal unstable triazoline.251 The decomposition products are 40% aziridine and 55% imide. Furthermore it has been observed that the rate of nitrogen evolution of the triazoline from methyl azidoformate increases threefold when triglyme and 20-fold when dimethyl sulfoxide are substituted for 1,1-diphenylethane as solvents. This fact supports a betaine intermediate in the thermal decomposition reaction. The triazoline from 2,4-dinitrophenyl azide and norbornene could just be isolated, but from picryl azide only the aziridine was obtained.252-254 Nevertheless, the high negative value of the activation entropy (—33.4 eu) indicates a similar cyclic transition state for both reactions. 

Isodrin (56) gives with f-butyl azidoformate an isolable triazoline (addition in position QQ) which decomposes into aziridine by chromatography over neutral alumina. 55 With tosyl azide, on the other hand, only the aziridine derivative could be isolated. Both aziridines undergo a series of transformations leading to a so-called bird-cage hydrocarbon 57. ... 

When ethyl azidoformate, cyanogen azide, or/CO(Ns)j is decomposed in benzene solution, no aziridipes/but azepines 111 are obtained.83M 98 101 324 32 The 7-azanorcaradienes (110) are most probably formed as unstable intermediates but rearrange immediately into the more stable azepines. 

Heterocyclic azides react with enamines31 1,8-naphthyridine azides give isolable triazolines.220 The bicyclic enamine 2-N-morpholinonorbornene with aryl and benzoyl azides furnishes stable, crystalline aminotri-azolines.39,213 Likewise, alkyl azidoformates yield stable triazolines.30,221... 

Amidines are also formed from less stable 1-hetaryl-220 and l-styryl-5-aminotriazolines.222,492,493 Thermolysis of the latter provides a method of synthesis of novel l-amino-2-azabutadienes (Scheme 176)492,493 Whereas cyanogen azide addition to dihydropyridines leads to bicycloazir-idines,241-243 addition of ethyl azidoformate yields the corresponding amidine 494 Likewise, indoles (103) react with picryl and sulfonyl azides to give... 

Bis(azidocarbonyl)cyclopropane, 1829 Bis(azidothiocarbonyl) disulfide, 1012 4-Bromobenzoyl azide, 2640 terf-Butyl azidoformate, 1930 A-Butylamidosulfuryl azide, 1687 Carbonic diazide, 0547 Carboxybenzenesulfonyl azide, 2695 4-Chlorobenzenesulfonyl azide, 2145 4-Chlorobenzoyl azide, 2650 /V-(2-Chloroethyl)-/V-nitrosocarbamoyl azide, 1128 Cyanodiazoacetyl azide, 1342 Cyanohydrazonoacetyl azide, 1080... 

H)-Oxazolones are formed by the spontaneous cyclization of /3-oxo isocyanates (equation 134). Similarly, o-hydroxyphenyl isocyanate, produced by the Curtius rearrangement of the azide of salicylic acid or by the action of sodium hypochlorite on salicylamide, forms benzoxazolone (equation 135). An analogous reaction is the formation of IV-phenyl-benzoxazolone by the action of thionyl chloride on the hydroxamic acid shown in equation (136) (78TL2325). Pyrolysis of aryl azidoformates affords benzoxazolones by nitrene insertion (equation 137) (81CC241). 

The thione carbon-sulfur bond in l,3-thiaselenole-2-thiones has been used as a dipolarophile for ethyl diazoacetate, phenyl azide and ethyl azidoformate (80JHC117). The proposed course of these reactions is illustrated for 5-phenyl-l,3-thiaselenole-2-thione (75)... 

OButyl azidoformate, a useful protective group for primary and secondary amino groups,4 0 has been prepared previously from f-butyl carbazate.3 The present procedure7 is a more convenient preparative method. 1 he intermediate carbonic phosphoric anhydride reacts with nucleophiles other than the azide ion in this preparation. Reaction of this anhydride with amines yields the t-butoxycarbonyl derivatives of amines.7 Other carbonic phosphoric anhydrides have been prepared by procedures analogous to the method described here.8... 

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