Sulphone-Fries rearrangement

Arylsulphonylmethyl sulphonates as photolytic products 882 Sulphone-Fries rearrangement 171 Sulphone metabolites, mass spectra of 153, 154... 

The availability of Nafion on silica has not only lowered the cost of the resin but also has made it versatile (Sun et al., 1997 Harmer et al., 1998). A number of industrially important reactions have been attempted, with considerable success, with these catalysts. Consider the Fries rearrangement of phenyl acetate to p-acetyl phenol (/t-hydroxy acetophenone). This has been accomplished by Hoelderich and co-workers (Heidekum, 1998). In the ca.se of alkylation of benzene with benzyl alcohol, Amberlyst-15 and p-toluene sulphonic acid are ineffective and Nafion on silica works well at 80 °C. 

Photo-Fries migration has been reported for the sulphonate ester (316) to give (317) A homolytic cleavage-recombination mechanism akin to the photo-Fries rearrangement of sulphonamldes may... 

As with acyl esters of phenols, the photochemical Fries rearrangement of aryl sulphonates is known. Thus, compounds 14a,b were photolysed at 300 nm for 12-24 h to... 

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. 

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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