Sultones thermal decomposition

However, certain additives can decrease the rate of thermal decomposition [28]. These additives include cyclic sulfates, sulfones, sultones, aliphatic and aromatic anhydrides, and polymers with pendant carboxylic acid functional groups. Most of these materials are latent acids, which decompose on heating in the presence of moisture to form a strong acid, as shown for cyclic sulfate, 9, in Eq. 5. 

The previous chapter in CHEC-II(1996) reported on the stability and derived thermochemical data for the isomerization of /3-sultones, the cycloreversion of 1,2-oxathietanes, the relative stability of 1,2- and 1,3-oxathietanes, the isomerization of 1,2-oxathietes, as well as aspects related to stereoisomerization <1996CHEC-II(1B)1083>. Unfortunately, no new studies or information has been presented over the last decade. The only experimental observation worthy of mention is that an equilibrium mixture of the thioketone 27 along with the 6-oxa-7-thiabicy-clo[3.1.1]heptane 28 was isolated in 48% yield from the thermal decomposition of a precursor dithiirane oxide <1997BCJ509>. This indicated that the activation barrier for cycloaddition-cycloreversion is low at ambient temperature. 

A few reports have appeared on the thermal decomposition of sultams. The thermolysis of unsaturated -sultams leads to formation of the corresponding pyrrole and indole derivatives (equation 233 and 234)291 and resembles the decomposition of the related sultones. The high-temperature pyrolysis of naphthosultam gives a mixture of 2- and 3-cyanoindenes (equation 235)292. On the other hand, the AZ-phenyl derivative forms the benzacridine 144 formed by loss of S02 and intramolecular trapping of the intermediate which forms (equation 236). Flash vacuum pyrolysis of the bicyclic sultam 145 gave a... 

Thermal decomposition of the p-sultone CFa CFg SOj-O, prepared from tetrafluoroethylene and sulphur trioxide, has been mentioned in the patent literature as a source of trifluoroacetyl fluoride and its decomposition in the presence of sulphuric acid has been claimed to yield difluoroketene (see p.40). 

The N-nitroso derivatives of propane sultam, butane sultam and pentane sultam were synthesized from the parent compounds (equation 230). N-nitrososultams decompose thermally in aqueous solution to form the corresponding sultones. However, just as in the case of sulphonamides, unless bases are present, a variety of reaction products are formed as a result of various (acid-catalysed) side-reactions. Reproducible rates of decomposition... 

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