4-Bromobenzenesulfonyl azide

Preparative Method by the reaction of 4-bromobenze-nesulfonyl chloride with excess sodium azide in a water-ethanol mixture.  

Handling, Storage, and Precaution should be used in solution. Azides are prone to violent detonation upon thermal, electrical, and mechanical shock. 

At high pressure ( kbar) the normally more sluggish i-butyldimethylsilyl enol ethers of cyclic ketones react in good yield to afford the ring contracted product (eq 3).  

The chemo-, regio-, and stereoselectivity of the ring contraction process has been demonstrated with a variety of dienol ethers obtained by dissolving metal reduction of aromatic methyl ethers (eqs 4 and 5).  

Dipolar Cycloaddition. The principal use of p-bromobenzenesulfonyl azide is in 1,3-dipolar cycloaddition reactions with functionally substituted alkenes. The reagent has been used at ambient temperature and pressure to convert simple trimethylsilyl and methyl enol ethers of cyclic ketones to ring-contracted p-bromobenzenesulfonimidates, and thence to the corresponding amides, esters, or acids (eqs 1 and 2). 

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Goldsmith and Soria (6b) reported a novel approach to a synthesis of the cyclopentanoid ring system 25 based on the 1,3-dipolar cycloaddition of p-bromobenzenesulfonyl azides with the electron-rich 1,4-cyclohexadienol ether 22 and subsequent ring contraction at moderate temperature (Scheme 9.6) (6a). 

An effect of sonication on the cycloaddition of sodium azide to aryl cyanides was observed, essentially a shorter time and an increased yield in the expected 5-aryltetrazples.i9 With the dipole 4-bromobenzenesulfonyl azide and vinyl-ethers as the dipolarophiles, excellent synthetic results were obtained (Fig. 6). ... 

Cycloaddition of jo-bromobenzenesulfonyl azide to alkynyl ethers affords equilibrium mixtures of triazole and diazocarbox-imidate. In the case of the ether in which both the carbon and the oxygen substituents of the alkynyl ether are methyl, only the triazole is found (eq 8). ... 

An equimolar mixture of 1-methoxy-l-cyclohexene and p-bromobenzenesulfonyl azide in abs. acetonitrile stored until spectroscopy shows the disappearance of the azide after several days or weeks product. Y 87%. F. e. s. R. A. Wohl, Tetrah. Let. 1973, 3111. 

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