Aryl derivatives s. a. Arenes

An example of a more structured aryl acetate is offered by the monoacetyl derivative 2 ofp-tert-butylcalix[4]arene-crown-5 (1). The half-life for deacetylation in the presence of 1 mM MeONMe4 in MeOH at 25 °C is 34 weeks, but drops to 8 s upon addition of 1 mM BaBr2 [17]. Also, SrBr2 accelerates the reaction, albeit to a somewhat smaller extent. Kinetic and UV spectroscopic data show that in the absence of metal ions MeO reacts with the unionized form 2, but in the presence of metal ions the reactive species is the metal complex of the ionized form 3, which is present in significant amounts by virtue of the acidity enhancing effect of the metal ion complexed by the polyether chain. 

The steroidal dienol triflate 284 in pyridine photo-extrudes S02 and forms the 6/ -trifluoromethyl derivative 285 presumably via a free radical reaction path257. The anhydride 286 undergoes S—O bond fission to afford radicals. When the reaction is carried out in aromatic solvents such as benzonitrile or nitrobenzene, hydrogen abstraction reaction or addition to the aryl groups of the solvent takes place256. Cadogan and Rowley259 report that the irradiation of the tosyloxy compounds 287 results in N—O bond fission to afford phthalimido radicals. These react with solvent (arene) to afford... 

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