Sulphonyl azides thermal decomposition

Uncatalyzed thermal decomposition of sulphonyl azides is believed to give nitrene intermediates and nitrogen, in general ... 

More recent work 8> shows that the S—N bond can be cleaved by hydroperoxides and that aromatic sulphonyl azides only undergo free radical thermal decomposition if a source of radicals is provided. Some light on the nature of the radical transfer agent has recently been shed by the observation 14> that dodecyl azides are formed (2.3%) in the thermolysis of mesitylene-2-sulphonyl azide (3) at 150 °C in w-dodecane under nitrogen. It seems likely that a dodecyl radical is produced by hydrogen abstraction by the triplet nitrene (5) [mesitylene-2-sulphonamide was also formed (1.1%)] which then attacks undecomposed sulphonyl azide... 

Ferrous chloride-hydrochloric acid mixtures catalyzed the thermal decomposition of sulphonyl azides in isopropyl alcohol to give occasionally almost quantitative yields of sulphonamide and acetone, and the molar ratio of azide consumed to ferric chloride formed was typically of the order of 20 to 1 21>. 

Copper catalyzes the decomposition of sulphonyl azides in benzene very slowly. When methanesulphonyl azide was boiled under reflux in benzene solution in the presence of an excess of freshly reduced copper powder, some decomposition occurred to give methanesulphonamide and azide was recovered 78>. Transition metal complexes have been found to exert a marked effect upon the yields of products and isomer ratios formed in the thermal decomposition of methanesulphonyl azide in methyl benzoate and in benzotrifluoride 36>. These results will be discussed in detail in the section on the properties of sulphonyl nitrenes and singlet and triplet behaviour. A sulphonyl nitrene-iron complex has recently been isolated 37> and more on this species will be reported soon. 

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... 

This present treatment is subdivided into the five major modes of decomposition acid-catalysed, thermal, trivalent phosphorus compound-catalysed, photolytic and transition metal-catalysed decompositions. Each section is further subdivided into alkyl, aryl and sulphonyl azide decomposition. The nature of the products formed and how these are affected by the nature of the reactive intermediates is discussed. 

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. 

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