Azides Azidotrimethylsilane

Recently Keumi et al. (1989) found that arenediazonium tetrafluoroborates readily decompose in the presence of azidotrimethylsilane in DMF solution to afford the corresponding aryl azides. 

Imino thioethers,2 The reagent, prepared in situ, converts the dimethyl thioketal of a cyclic ketone (2) into the imino thioether 3 in high yield. The reaction can also he carried out with azidotrimethylsilane (1 equivalent), stannic chloride (1 equivalent), and iodine (10 mole %). but yields arc lower. This reaction was examined because of the reaction of thiokctals with iodine azide (this volume). 

Azidotrimethylsilane, 24, 217 Diazidodiisopropoxytitanium, 217 Sodium azide-Methyltrioctylammonium chloride, 240 Aziridines... 

Azidotrifluoromethane, see Trifluoromethyl azide, 0346 f Azidotrimethylsilane, see Trimethylsilyl azide, 1310... 

In 1991, Duncia et al. reported on the synthesis of 1,5-disubstituted tetrazoles from secondary amides and azidotrimethylsilane under the conditions of the Mitsunobu reaction <1996CHEC-II(4)621>. The Mitsunobu protocol was successfully applied to the conversion of AT(cyanoethyl)amide into tetrazole 510. The tetrazole ring in this event forms by the cyclization of an imidoyl azide (not shown in the scheme) whose precursor is the phosphonium imidate 509 (Scheme 67) <2000JME488>. 

Azido alcohols.1 This azide is considerably more reactive for cleavage of epoxides than azidotrimethylsilane, which requires a Lewis acid promotor. Although DMF enhances the reactivity of the silyl azide, it lowers the reactivity of the stannyl azide. The reactivity of the latter azide is also decreased by neighboring ester, acetonide, or ether groups. 

Alkylaryl azides.3 Reaction of an alkylarene with DDQ and N3Si(CH3)3 in CHC13 at 25° results in replacement of a benzylic hydrogen by an azide group to give an alkylaryl azide in 50-95% yield. Hydrazoic acid can be used in place of azidotrimethylsilane, but this reaction is generally slower. 

Caution Parts A and C of this procedure should be carried out in a well-ventilated hood since toxic hydrogen bromide and azidotrimethylsilane are handled and toxic hydrogen azide is liberated during the course of the reaction. 

The reaction of azidotrimethylsilane and ethanol, which gives hydrogen azide and ethoxytrimethylsilane, is exothermic and the hydrogen azide immediately forms a salt with 4-(dimethylamino)pyridine, a part of which cannot be dissolved in N,N-dimethylformamide and precipitates. 

For the azide cleavage of chiral 2,3-epoxy diester 3, the submitter s earlier procedure81 was modified to reduce the amount of azide reagent (azidotrimethylsilane, TMSN3) and lower the reaction temperature. This effort, coupled with the submitter s recent finding that such a reaction can be accelerated in the presence of amines,89,9 led to the use of the system described above. The reaction may proceed by way of the... 

The reaction of an exocyclic methylene group with 7V-phenylselcnophthalimide (A -PSP) and azidotrimethylsilane affords cyclic / -phenylseleno-substituted azides (Table 10)97. 

Hydrazoic acid is conveniently prepared in situ by hydrolysis of azidotrimethylsilane over silica gel. Only a catalytic amount of trifluoromethanesulfonic acid is required to achieve the hydroazidation of cyclic alkenes the completion of the reaction is preferentially controlled by gas-chromatographic analysis, as prolonged reaction time causes the partial decomposition of the organic azide by the acid catalyst. From norbornene the exo-azide 5 was exclusively produced, but no diastereoselectivity was observed with 1,2-dimethylcyclohexene106. 

Halo and 0-Trifluoroacetoxy Azides From Reaction with Azidotrimethylsilane... 

Diazides were less selectively prepared by the reaction of alkenes with azidotrimethylsilane and lead tetraacetate (see also Section 7.2.2.6.) or with anodically generated azide radicals75. 

Allylic azides, e.g., 1, were produced by treatment of the triisopropylsilyl enol ethers of cyclic ketones with azidotrimethylsilane and iodosobenzene78, but by lowering the temperature and in the presence of the stable radical 2,2,6,6-tetramethylpiperidine-/V-oxyl (TEMPO), 1-triso-propylsilyloxy-l,2-diazides, e.g., 2, became the predominant product79. The radical mechanism of the reaction was demonstrated. A number of 1,2-diazides (Table 4) were produced in the determined optimum conditions (Method B 16h). The simple diastereoselectivity (trans addition) was complete only with the enol ethers of unsubstituted cycloalkanones or 4-tert-butylcy-clohexanone. This 1,2-bis-azidonation procedure has not been exploited to prepare a-azide ketones, which should be available by simple hydrolysis of the adducts. Instead, the cis-l-triiso-propylsilyloxy-1,2-diazides were applied to the preparation of cw-2-azido tertiary cyclohexanols by selective substitution of the C-l azide group by nucleophiles in the presence of Lewis acids. 

Lead acetate azides, Pb(OAc)4 (N3)n, prepared in situ from lead tetraacetate and azidotrimethylsilane, react with alkenes to yield a variety of products, depending on the structure of the alkene 1,2-diazides. 1,2-acetoxy azides, a-azido ketones, allylic azides, and <5-oxo nitriles (by the oxidative cleavage of cyclohexene rings)97. The diazides and acetoxy azides are formed by preferential syn addition, but the diastereoselectivity (up to 3 1) is far from satisfactory with both acyclic and cyclic alkenes98,99. 

The direct azido phenylselenenylation of alkenes can be accomplished by four different methods A126 reaction with phenylselenenyl chloride and sodium azide in dimethyl sulfoxide or dimethylformamide B127 reaction with diphenyldiselenide, sodium azide and iodosobenzene diacetate in dichloromethane C128 reaction with iV-phenylselenophthalimide (TV-PSP) and azidotrimethylsilane in dichloromethane D128 as in C but in the presence of 0.1 equivalent of tetrabutylammonium fluoride. 

Halide and Azide Anions. These also open the epoxide re-gioselectively at the C-3 position. Addition of Li2CuBr4 results in bromide addition at the C-3 position of rac-(l), forming 3-bromo-1,2-propane 1-0-tosylate in 70-76% yield in THF or acetonitrile at It, or 1,3-dibromo-2-propanol in 82% yield in refluxing acetonitrile. Hydrofluorination takes place with KHF2 under solid-liquid phase transfer conditions, but the yield of fluorohydrin is very low (eq 3). Azidotrimethylsilane adds in the presence of a Lewis acid catalyst (eq 3). Addition of cyanide ion is achieved by using Diethylaluminum Cyanide in toluene. ... 

Azidotrilluoromctlianc. see Trilluoromctliyl azide, 0347 Azidotrimethylsilane, see Trimethylsilyl azide, 1314 Azinphosmethyl, see (9,(9-Dimethyl-S-[(4-oxo-l,2,3-benxotriazin-... 

Azidation of alkenes.1 Trifluoromcthancsulfonic acid is an efficient catalyst for addition of hydrazoic acid to alkenes. The reaction is also facilitated by silica gel or alumina. A further advantage is that these adsorbents can effect in situ hydrolysis of azidotrimethylsilane to hydrazoic acid, HNj. This new procedure is particularly useful for preparation of tertiary, bcnzylic, and allylic azides. 

Primary alkyl amines. a-Alkoxy azides are reduced to primary amines by lithium aluminum hydride in ether. A side reaction noted occasionally, reduction to an ether, can be suppressed by addition of TMEDA. Sodium bis(2-methoxy-ethoxy)aluminum hydride cannot replace lithium aluminum hydride in this reductive amination. The a-alkoxy azides are available by reaction of aldehydes with azidotrimethylsilane, by addition of hydrazoic acid to an enol ether, or by reaction of ketals with the l8-crown-6 complex of sodium azide. 

Azanaphthalene iV-oxides undergo photochemical deoxygenation reactions in benzene containing BF3 OEt2, resulting in amines in 70-80% yield these amines are important in the synthesis of heterocyclic compounds. Azidotrimethylsilane reacts with traws-1,2-epoxy alky Isilanes in the presence of BF3-OEt2 to produce (Z)-l-alkenyl azides. The cis-1,2-epoxyalkylsilanes undergo rapid polymerization in the presence of Lewis acids. 

Aryl and vinyl azides can also be accessed in one step from the corresponding halides or triflates via a copper-catalyzed reaction with sodium azide in the presence of a catalytic amount of L-proline (Scheme 7.5C) [104]. In this fashion, a range of 1,4-disubstituted 1,2,3-triazoles can be prepared in excellent yields [105-107]. Anilines can also be converted to aryl azides by the reaction with tert-butyl nitrite and azidotrimethylsilane [108]. The resulting azides can be submitted to the CuAAC conditions without isolation, furnishing triazole products in excellent yields. Microwave heating further improves both reactions, significantly reducing reaction time [56, 62]. 

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