From Sulphonyl Azides

The production of the nitrenes from a variety of sources has been reported, the most common of which are the sulphonyl azides. 

Starting materials other than sulphonyl azides have been used as possible sources of sulphonyl nitrenes. The decomposition of the triethyl-ammonium salt of iV- -nitrobenzenesulphonoxybenzenesulphonamide (26) in methanol, ethanol, and aniline gave products derived from a Lossen-type rearrangement 20> (Scheme 3). It was felt that the rearrangement did not involve a free sulphonyl nitrene since, when the decomposition was carried out in toluene-methylene chloride or in benzene, no products (benzenesulphonamides) of substitution of the aromatic solvent nucleus were found (as are usually found with sulphonyl nitrenes from the thermal decomposition of the corresponding azides). On the other... 

The decomposition of organic azides has been studied from a number of points of view, the objectives being mainly synthetic or mechanistic. The nature of the intermediates formed have received much attention. In this chapter we shall consider the decomposition of alkyl, aryl and sulphonyl azides under various conditions. Acyl and vinyl azides are considered elsewhere in this volume. 

In agreement with equation (109), recent work has shown that the thermolysis (150°) under nitrogen of mesitylene-2-sulphonyl azide (251) in n-dodecane gave rise to dodecyl azides (2 3%) This was thought to occur by the triplet nitrene (253) abstracting a hydrogen from the solvent to produce C12H25 which could then attack azide (251) to produce an alkyl azide and 254 °. The same products... 

A great deal of interesting work was carried out by Curtius and co-workers , who first studied the thermolysis of sulphonyl azides. Some of the work certainly deserves reinvestigation using modem analytical tools. For example, the report that 272 and 273 were obtained from decomposition of sulphonyl azide in />-xylene must be viewed with scepticism, but it would certainly be interesting to determine the correct structures of the products formed. 

Vinyl ethers also react readily with sulphonyl azides to give imino-esters. For example, from dihydropyran and j -toluenesulphonyl azide, the arylsulphonylimine of S-valerolactone (290) was obtained in quantitative yield... 

TV -Sulphonyliminolactones have been obtained directly in this manner from 64 and sulphonyl azides . 

Although thermolysis of triazoline can also, in certain cases , lead to aziridines, mixtures with azomethines usually result, and the photochemical process is preferable. The triazolines formed from acyl ° or sulphonyl azides are unstable and the corresponding aziridines can be obtained directly. The reaction of norbomene and benzoyl azide at 40° yielded the aziridine (128) directly... 

Nitrenes were first proposed as reactive intermediates in the Lossen rearrangement by Tiemann in 1891, and subsequently by Stieglitz (1896) to account for the mechanisms of the related Hofmann, Curtius, and Beckmann rearrangements. Apart from an extensive amount of work by Curtius on the thermal decomposition of aryl and sulphonyl azides, interest in nitrenes declined until the reemergence of carbene chemistry in the 1950s. Reviews on nitrene chemistry by Kirmse (1959), Horner (1963), and Abramovitch (1964) reflected this renewed interest in nitrenes and provided a stimulus for the immense research effort undertaken in the 1960s, which has been surveyed in many reviews and two books.Of particular note are two chapters by Abramovitch" describing all facets of nitrenes, and an excellent chapter devoted specifically to aryl- and hetarylnitrenes by P. A. S. Smith. The present chapter is intended to update these reviews and it is hoped that it will stimulate further work, particularly on the synthetic aspects of intermolecular arylnitrene reactions. 

The synthesis of azidocyclopropanes has been accomplished with varying success via the nitrogen transfer reaction from toluene-p-sulphonyl azide to cyclopropylamine anions or by the addition of carbenes or carbenoids to vinyl azides. 

In a related piece of work, imidazolines have been prepared from A -chloro-N-phenyl amidines and enamines. (Scheme 79). Pyrazomycins have been synthesized by the Roche group, the key step being the preparation of the pyrazolone ring by the addition of toluene- -sulphonyl azide to the anion from diethyl acetone dicarboxylate (Scheme 80). Imidazolidines (201) have been prepared by the action of isocyanates and isothiocyanates with an aziridine ester a dipolar intermediate is implicated. Imidazolidine-4,5-diones have been prepared by the... 

Normally, decompositions of azides in hydrogen-rich solvents are avoided in order to minimize the formation of products based on triplet nitrene. Surprising, therefore, is the report that 6i/-dibenzo[c ,e][l,2]thiazine 5,5-dioxide (335) is obtained in optimum yield (80.6%) from the thermolysis of biphenyl-2-sulphonyl azide in cyclohexane at 120 Decomposition of o-(2-thienyl)benzenesul-phonyl azide under similar conditions furnishes the thieno[3,2-c]benzo-l,2-thiazine dioxide (336), in practicable yield (61%). Whereas, in POCla-pyridine... 

Sulphonyl Azides.—The generation of a sulphonylnitrene from the corresponding sulphonyl azide in solution, followed by attack on the solvent, accounts for the various mixtures of reaction products obtained. The simplest sulphonyl azides continue to be used, though more complex examples, e.g. o-dialkylaminobenzene-sulphonyl azide and o- and p-benzenedisulphonyl azides, have been studied. 

On the other hand, thermolysis of ferrocenylsulpkonyl azide (14) in aliphatic solvents may lead to the predominant formation of the amide (16) 17>. A 48.4% yield of (16) was obtained from the thermolysis in cyclohexane while an 85.45% yield of 16 was formed in cyclohexene. Photolysis of 14 in these solvents led to lower yields of sulphonamide 32.2% in cyclohexane, 28.2% in cyclohexene. This suggests again that a metal-nitrene complex is an intermediate in the thermolysis of 14 since hydrogen-abstraction appears to be an important made of reaction for such sulphonyl nitrene-metal complexes. Thus, benzenesulphonamide was the main product (37%) in the copper-catalyzed decomposition of the azide in cyclohexane, and the yield was not decreased (in fact, it increased to 49%) in the presence of hydroquinone 34>. On the other hand, no toluene-sulphonamide was reported from the reaction of dichloramine-T and zinc in cyclohexane. 

Aryloxysulphonyl azides are obtained in good yield from the reaction of the sulphonyl chloride with tetra-n-butylammonium azide [11]. 

The syntheses of the pachysandrines and epipachysandrine-A have been effected starting from the diosphenol (214). Reduction of (214) with sodium borohydride leads to an epimer of terminaline, 3)8,4 -dihydroxy-20a-dimethyl-amino-5a-pregnane (221), which readily forms a mono-tosylate (222) on treatment with toluene-p-sulphonyl chloride in pyridine. On treatment with sodium azide in N-methylpyrrolidone, the mono-tosylate (222) gives the azide (224) with... 

Some of the more important reactions of the aziridines cire set out in the following equations. The v/c-diamine can also be prepared from an epoxide by successive reaction with sodium azide, methane-sulphonyl chloride, sodium azide and hydrogen/ platinum. 

Details have appeared on the behaviour of methyl 2,3-0-isopropylidene-4-0-toluene-p-sulphonyl-a-D-lyxo- and -P-L-ribo-pyranoside towards nucleophiles (see Vol. 8, p. 53). The dithiepane derivatives (127) and (128) were formed via the intermediate (126), resulting from sulphur migration, when the mesylate (125) was treated with sodium azide in warm DMF ° (see also Chapter 15). The reactions of... 

---