Styrenes azido

Oliveri-Mandald found that HN3 adds to benzoquinone to give azido-hydroquinone [44]. Extension of this reaction to acetylenes led to triazoles [45] and failed entirely with cinnamic acid, fumaric acid, styrene, vinyl bromide, ethylene, and other olefinic compounds [46]. 

McEwen et al. hydrogenated 2-azido-2-phenylethanol, prepared by the reaction of styrene oxide with sodium azide, over platinum oxide in ethanol to give 2-amino-2-phenylethanol in 81% yield (eq. 9.93).245... 

Addition to alkenes. Hydrazoic acid ados readily to cnol ethers to give a-azido ethers. Addition to styrenes and 1,1 -disubstituted or trisubstituted alkenes requires a Lewis acid catalyst (TiC or AlCl,). Benzylic, allylk. and tertiary alcohols react with HN, TiCl4 to form azides. 

Styrene oxide undergoes attack at the benaylic epoxide carbon Atom exclusively (Eq. 001), giving 2-azido-2>phenylethanoI as eole product. M ... 

Another approach for the preparation of organic polymers with cyclophos-phazene side groups involves the Staudinger reaction of an azido- substituted cyclophosphazene with a phosphine residue in an organic copolymer. Free-radical copolymerization of styrene with diphenyl-p-styrylphosphine yields... 

Thermolysis of terminal vinyl azides has generally led to the isolation of products other than azirines. A number of j8-azido-styrene derivatives have, on pyrolysis, yielded indoles. Thus /S-azido-a-methylstyrene, (60) when boiled in mesitylene, produced an 80% yield of 3-methylindole (61) and 9% of a-phenylpropionitrile (62) Decomposition of the same compound in ethanol, however, gave only a trace of the indole the major product, isolated in about... 

Generation. By the reaction of an aqueous suspension of silver azide and an ethereal solution of iodine. Hantzsch obtained the reagent us an unstable solid. Hassner and Levy generated the pseudohulogen more conveniently from iodine monochloride and sodium azide in DMF or acetonitrile solution and found that it adds stereospecifically to olefins. Thus A -cholestene is converted info the tran.%-diaxiul 2/I-azido-.la-iadocholesliine. Yields of adducts fh>m cyclohexenc, styrene, W.v- and trnn.v-stllbene were HO, 70, fi.I, and 80%. 

Another facile reagent combination is the Pb(OAc)4-TMSA system that gives access to a-ketoazides e.g. an a-azido-cyclohexanone 484) can be obtained (Scheme 68) and a-azido-acetophenone 485) from styrene " using the slightly modified C6HsI-(OAc)2-TMSA reagent system. 

Thermolysis of orffto-azido-styrenes gives nitrenes that insert into the side-chain to form indoles. Similar nitrenes have been generated by reaction of nitro-compounds with trialkyl phosphites. The azide thermolysis method can be used to prepare 2-nitroindoles. ... 

In a complementary sense, thermolysis of P-azido-styrenes also gives indoles, but here the intermediate may be an azirine ° this method, the Hemetsberger-Knittel synthesis, is particularly useful for the fusion of a pyrrole ring onto rings other than a benzene ring, as illustrated. ... 

The introduction of an azide functionality with CAN/NaNs as the reagents has been shown to be a useful transformation in organic synthesis. It also offers a convenient protocol for the bis-functionalization of a variety of alkenes. " The treatment of silyl enol ethers with sodium azide and CAN gives the a-azido ketones. The reactions of (substituted)styrenes with sodium azide and CAN in methanol under oxygenated conditions also furnish a-azido ketones (eq 21). With the aid of sodium iodide. 

Tsarevsky has found that hypervalent iodine compounds can be used for the direct azidation of polystyrene and consecutive click-type functionalization [49]. In particular, polystyrene can be directly azidated in 1,2-dichloroethane or chlorobenzene using a combination of trimethylsilyl azide and (diacetoxyiodo)benzene. 2D NMR HMBC spectra indicate that the azido groups are attached to the polymer backbone and also possibly to the aryl pendant groups. Approximately one in every 11 styrene units can be modified by using a ratio of PhI(OAc)2 to trimethylsilyl azide to styrene units of 1 2.1 1 at 0 °C for 4 h followed by heating to 50 °C for 2 h in chlorobenzene. The azidated polymers have been further used as backbone precursors in the synthesis of polymeric brushes with hydrophilic side chains via a copper-catalyzed click reaction with poly(ethylene oxide) monomethyl ether 4-pentynoate [49],... 

Preparations of azide derivatives from styrene-maleic anhydride copolymers, cellulose, and gelatin by attaching aromatic azide compounds are described in the literature. Most of the resultant polymers crosslink rapidly when exposed to light of 260 wavelength. Also, as much as 90% of the hydroxy groups of poly(vinyl alcohol) can be esterified withp-azido-benzoyl chloride. These reactions must be carried out in mixtures of chloroform and aqueous sodium hydroxide. Based on infrared spectroscopy, the following crosslinking mechanism was proposed ... 

Using the rst approach, Sumerhn and coworkers (Gondi et al., 2007) synthesized functional telechelic polymers for which two novel azido-functionalized chain trasfer agents (CTAs), namely, (Xn) and (XIII) (see Fig. 12.18), were prepared and employed to mediate the RAFT polymerization of styrene (St) and Af,Af-dimethylacrylamide (DMA) under a variety of conditions. Poly-... 

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