Arenesulphonates rearrangement

TABLE 1. Isomer distribution for the rearrangement of some arenesulphonic acids... 

Arenesulphonate salts undergo rearrangement on heating, but there has been no subsequent work reported since this area was last reviewed1. 

In contrast to these observations, Snell studied the photo-Fries rearrangement of sulphonate esters of 6-substituted 4-hydroxypyrimidines (equation 9) and found efficient conversion for a variety of alkane- and arenesulphonates [e.g. R1 = Me, Et, Bu, (CH2)3C1, Ph, 4-Tol, 4-ClC6H4, 4-BrC6H4, 4-An, 2,5-Me2C6H3, 2,4,6-Me3C6H2]47. Yields vary between 20-60%, and the reaction does not proceed for R3 = NH2 or NHAc. The reaction has synthetic utility, since the product sulphones are inaccesible via the Friedel-Crafts procedure. 

Preparations from sulphinic acids, SO2, other simple sulphur compounds, and sulphonyl halides are reported in the papers that are listed (with brief details) at the end of this section. The AlClj-catalysed rearrangement of an aryl arenesulphonate gives the corresponding diaryl sulphone. ... 

Sulphonates.—Novel syntheses are reported for methyl arenesulphonates (activated benzene + Me03SF at 100 C) and more generally," employing R C0P(0)(0R 2 for esterification of sulphonic acids. A photo-Fries rearrangement (76) (77) is notable." ... 

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