Of phenyl azide

Addition on to the exocyclic C—C double bond of an alkylideneaziridine also occurs when this compound is allowed to react with organic azides (75JOC2045). The initially formed spirotriazolines (332) are converted into four-membered ring amidines (334) with extrusion of molecular nitrogen. In the case of phenyl azide, the amidine (334) is obtained alongside the triazoline (333). 

The additions of phenyl azide and phenylnitrile oxide to pentafluorophenyl-acetylene are also regiospecific [75, 7S] (equation 12). Interestingly, in the latter reaction, phenylacetylene gives regiochemistry that is opposite to that observed for pentafluorophenylacetylene [75]... 

The mechanism of the cycloaddition of phenyl azide to norbornene has been shown to involve a concerted mechanism with a charge imbalance in the transition state (199). In a similar manner the cycloaddition of phenyl azide to enamines apparently proceeds by a concerted mechanism (194, 194a). This is shown by a rather large negative entropy of activation (—36 entropy units for l-(N-morpholino)cyclopentene in benzene solvent at 25°C), indicative of a highly ordered transition state. Varying solvents from those of small dielectric constants to those of large dielectric constants has... 

The addition of phenyl azide to diacetylene in benzene at 20-70°C has been performed (79KGS849). Depending on the amount of phenyl azide, 1-phenyl-4(5)-ethynyl-1,2,3-triazoles (96) and 4,4 -di(l-phenyl-1,2,3-triazoles) (97) were obtained in 64 and 55.5% yield, respectively. 

Friesner and coworkers investigated the 1,3-dipolar addition of phenyl azide 60 to carbon-carbon double bonds forming l-phenyl-4,5-dihydro-l//-l,2,3-triazoles (61 and 62) (Scheme 39) [99JPC(A)1276]. 

Generation of phenylnitrcne by thermal decomposition of phenyl azide in the same solvent mixture, or by deoxygenation of nitrosobenzene with triethyl phosphite in the absence of the trifluoroethanol, fails to yield the 1//-azepine. The role of the alcohol in promoting l//-azepine formation is not understood. 

The thermal, and more importantly, the photolytic decomposition of aryl azides in the presence of nucleophiles, generally amines or alcohols, is the commonest method for preparing 3H-azepines. In fact, jV-phenyl-3//-azepin-2-amine (32, R = Ph), the first example of a 3//-azepine, was prepared by thermal decomposition of phenyl azide in aniline.32... 

Pioneering studies have shown that the yield of iV-phenyl-3//-azepin-2-amine (32, R = Ph) from the thermolysis of phenyl azide in aniline increases as the ratio of azide to aniline decreases, and in dilute solution with an azide to aniline ratio of 1 200 a 54% yield of the 3//-azepine can be achieved.34 The reaction is successful with other arylamines, but the procedure is of limited preparative value as large volumes of amine are required and only moderate yields of 3H-azepines are obtained. 

Likewise, thermolysis of 4-azidophenyl methyl ketone in methanol yields 5-acetyl-2-methoxy-3//-azepine (60%), compared to only an 8% yield from the photolytic reaction.78 119 The thermolysis of phenyl azide in refluxing cyclohexanol yields no 3H-azepine, only diphenyl-diazene (10%) and aniline (30%).74 In contrast, thermolysis of methyl 2-azidobenzoate in cyclohexanol furnishes a mixture of methyl 2-(cyclohexyloxy)-3//-azepine-3-carboxylate (20 % bp 127°C/0.1 Torr) and methyl 2-aminobenzoate (60%). Thermolysis of the azido ester in methanol under nitrogen in an autoclave at 150 C yields a 7 10 mixture (by 1HNMR spectroscopy) of the amino ester and methyl 2-methoxy-3//-azepine-3-carboxylate, which proved to be difficult to separate, and much tar.74 The acidic medium179 is probably responsible for the failure of methyl 2-azidoberjzoate to yield a 3//-azepine when thermolyzed in 3-methoxyphenol aniline (40%) is the major product.74... 

Interestingly, photolysis of phenyl azide in liquid ammonia yields 3//-azepin-2-amine (39)35 (see experimental procedure in Houben-Weyl, Vol.4/5b, pi268). 

Photolysis of aryl azides in amine solution, with a tertiary amine as cosolvent to promote stabilization of the singlet nitrene, has met with some success. For example, the yield of 2-piperidino-3 W-azepme. obtained by the photolysis of phenyl azide in piperidine, is increased from 35 to 58% in the presence of A A /V. /V -tetramethylethylenediamine (TMLDA).180 Also, an improved yield (36 to 60 %) of A,(V-diethyl-3W-azepin-2-amine (38, R = Et) can be obtained by irradiating phenyl azide in triethylamine, rather than in dicthylaminc, solution.181 Photolysis (or thermolysis) of phenyl azide in TMEDA produces, in each case, 38 (R = Et) in 40% yield.181 In contrast, irradiation of phenyl azide in aniline with trimethylamine as cosolvent furnishes jV-phenyl-377-azepin-2-amine (32, R = Ph) in only low yield (2%).35... 

Early efforts to effect the photoinduced ring expansion of aryl azides to 3H-azepines in the presence of other nucleophiles met with only limited success. For example, irradiation of phenyl azide in hydrogen sulfide-diethyl ether, or in methanol, gave 17/-azepine-2(3//)-thione35 (5% mp 106—107 " O and 2-methoxy-3//-azepine (11 %),2 3 respectively. Later workers194 failed to reproduce this latter result, but found that in strongly basic media (3 M potassium hydroxide in methanol/dioxane) and in the presence of 18-crown-6, 17/-azepin-2(3//)-one was produced in 48% yield. In the absence of the crown ether the yield of azepinone falls to 35%. 

Attempts to effect ring expansion of methyl 2-azidobenzoate in the presence of other nucleophiles have failed. Thus, photolysis in tetrahydrofuran solution saturated with hydrogen sulfide, or with ammonia, produced methyl 2-aminobenzoate in 54 and 37 % yield, respectively, as the sole identifiable product.197 Photolysis of phenyl azide in ethanolic phenol gave 2-phenoxy-3//-azepine in poor yield (8 %).203,204 2-Mesityl-3//-azepine (10 %) is the surprising, and only tentatively explained, product from the photolysis of phenyl azide in mcsitylene in the presence of trifluoroacetic acid.179... 

The kinetics of 1,3-dipolar cycloaddition of phenyl azide to nor-bornene in aqueous solutions was studied (Eq. 12.67).145 As shown in Table 12.1, when the reaction was performed in organic solvents, the reaction showed very small effects of the solvent, while in highly aqueous media, significant accelerations were observed. 

Quantitative formation of 118-phenyldihydrotriazole (II) by heating Compound 118 with an excess of phenyl azide liquid, in absence of solvent, and then removing unreacted azide with a mechanical vacuum pump. (Because of the small amounts of 118 and phenyl azide reacting, the presence of conveniently measured amounts of solvent makes the rate of dihydrotriazole formation too slow to be practicable.)... 

Procedure. A hexane solution of Compound 118 is diluted or concentrated so as to bring the 118 content within a range of 15 to 150 micrograms per ml. In cases where the hexane solution requires concentration, the evaporation is carried out in a beaker on a steam bath with a gentle stream of air passing over the surface. The concentrated or diluted solution of 118 is washed with hexane into a volumetric flask and made up to volume with the hexane washings. One milliliter of the adjusted Compound 118 solution is precisely measured into a spectrophotometer cell, 2 drops of phenyl azide are added, and the dihydrotriazole is quantitatively formed and then treated with diazotized dinitroaniline to produce the red color as in the preparation of the standard curve. A blank, starting with 1.0 ml. of hexane and 2 drops of azide, is run at the same time. 

On heating, phenyl azide decomposes partially to give nonvolatile products which form colors with diazonium compounds. To minimize the presence of these impurities, the quantity of phenyl azide is limited to 2 drops in the triazole formation step. 

It appears that the decomposition of phenyl azide is significantly accelerated by direct exposure to light. Consequently, during all steps of the procedure in which phenyl azide is present, including that of its removal in vacuo, exposure of the reaction mixtures to direct light must be avoided. 

From the manipulative standpoint, the critical step lies in the vacuum evaporation of the solvent from the solution of Compound 118 and the two drops of phenyl azide. Care must be observed that no foaming or undue chilling occurs during the evaporation undue chilling may cause some Compound 118 to crystallize out of contact with the phenyl azide and prevent quantitative formation of the dihydrotriazole. 

An alternative explanation, based on a spectroscopic study involving an argon matrix, has been advanced to account for the singlet photochemistry of phenyl azide (457).381 The primary photoproduct is believed to be 1-azacyclohepta-l,2,4,6-tetraene (458). A separate but later study suggests that... 

The following operations should be done using standard safety procedures for working with radioactive compounds. All steps involving SASD prior to initiation of the photoreaction should be done protected from light to avoid loss of phenyl azide activity. The radiolabeling procedure should be done quickly to prevent excessive loss of NHS ester activity due to hydrolysis. 

Meijer, F.W., Nijhuis, S., and Vroonhoven, F.C.B.M. (1988) Poly-1,2-azepines by the photo-polymerization of phenyl azides. Precursors for conducting polymer films./. Am. Chem. Soc. 110, 7209-7210. 

The initially obtained product undergoes isomerization and then the addition of phenyl azide to the phosphorus atom takes place. It is proposed that the oxidative imination does not depend on the steric effects of substituents. Actually, the interaction of 5-phenyl-2,4,6-triisopropyI-1,3,5-dioxaphosphorinane, existing as a mixture of three stereoisomers, gives with phenyl azide a mixture of three stereoisomers of 5-phenyl-5-phenylimino-2,4,6-triisopropyl-l,3,5-dioxaphosphorinane (83IZV2550). 

A. 1,4-Diphenyl-5-amino-l,2,3-triazole. A 500-ml. three-necked flask is equipped with a sealed stirrer, a thermometer well, and a dropping funnel which is protected by a drying tube and has a pressure-equalizing side arm. A mixture of 35.7 g. (0.3 mole) of phenyl azide (Note 1) and 38.6 g. (0.33 mole) of phenylacetonitrile (Note 2) is placed in the flask. The flask is immersed in an ice-water mixture contained in a 1-gal. Thermos flask. After the reaction mixture has cooled to about 2°, a solution of 24.3 g. (0.45 mole) of sodium methoxide (Note 3) in 150 ml. of absolute ethanol is added dropwise during the course of 2 hours. The reaction mixture is then stirred at 2-5° in the ice-water bath for a period of 48 hours (Note 4). After the cooling bath has been removed and the flask allowed to warm spontaneously to room temperature, the mixture is filtered by suction on a sintered glass funnel, and the col-... 

Electron-rich aromatic compounds, such as phenol, anisole and A,./V-dimethylaniline, add to bis(2-trichloroethyl) azodicarboxylate under the influence of lithium perchlorate, boron trifluoride etherate or zinc chloride to yield para-substituted products 74, which are transformed into the anilines 75 by means of zinc and acetic acid86. Triflic acid (trifluoromethanesulphonic acid) catalyses the reactions of phenyl azide with benzene, toluene, chlorobenzene and naphthalene, to give TV-arylanilines (equation 34)87. 

Phenyl-7-azabicyclo[U,l,0]heptane 20G of phenyl azide and 20g of cyclohexene in 50ml of tetrahydrofuran were refluxed for 8 hours. Triazoline was obtained by distilling off the solvent and the unreacted components. 3G of triazoline was dissolved in 100ml of benzene and irradiated with a 100 watts high pressure mercury lamp for 5 hours. After irradiation, benzene was distilled off. 7-Phenyl-7-azabicyclo[U,l,0]heptane was obtained as the residue. 

The thermal cycloaddition of azides to acetylenes is the most versatile route to 1,2,3-triazoles, because of the wide range of substituents that can be incorporated into the acetylene and azide components. The accepted mechanism for the reaction is a concerted 1,3-dipolar cycloaddition. The rates of addition of phenyl azide to several acetylenes have been measured the rates of formation of the aromatic triazoles are not appreciably different from the rates of cycloaddition to the corresponding olefins, indicating that the transition-state energy is not lowered significantly by the incipient generation of an aromatic system. 

A very bulky group, such as trimethylsilyl, tends to occupy the 4-position. Addition of phenyl azide to phenyltrimethylsilylacetylene gives almost exclusively the 4-trimethylsilyltriazole. This can be useful because of the ease of removal of trimethylsilyl substituents. Additions to diacetylenes and addition of p-diazidobenzene to 1,4-diethynylbenzene are also claimed to be regiospecific. 

An example of the reaction of an azide with an allene is known the cycloaddition of phenyl azide to cyanoallene, which gives 4-cyano-5-methyl-l-phenyltriazole. °... 

Phenylazide was first synthesized by Greiss in 1864. In 1912, Wolf studied the pyrolysis of phenyl azide in aniline. The product of this reaction, azepine (27), was identified by Huisgen and co-worker in 1958. Eight years later. Doering and Odum demonstrated that azepine (27) is formed upon photolysis of phenylazide in diethylamine and in 1977 Carroll et al. ° discovered the formation of 28 upon photolysis of phenyl azide in the presence of ethanethiol. 

This finding led to general acceptance of the view that either azirine (29) and/or ketenimine (30) are the trappable reactive intermediates produced upon photolysis of phenyl azide in solution. ... 

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