From polyfluoro-aromatic compounds

The steric requirements of the ligands in lO.llA are considerable and this feature has allowed a number of unusual systems to be synthesised [48]. 

Metallation of less highly fluorinated systems has been reviewed [49]. 

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Generally, polyfluoro-aromatic compounds and polyfluoroalkenes are not particularly susceptible to electrophilic attack and, consequently, electrophilic cleavage of these groups from metals, which in some cases occurs very rapidly, is of considerable interest. 

Fluoroalkyl chromone derivatives can be obtained from the base catalysed reaetion between 2,2-dihydropolyfluoroalkanoates and phenols. Initial loss of HF allows Michael addition of the phenol and subsequent cyclisation of the enol ether yields the heterocycle. m-Substituted phenols give the expected mixture of 5- and 7-substituted chromones, whilst dihydroxy aromatic compounds give polycyclic materials (94JFC263). In a more conventional approach Z-3-(aryloxy)-polyfluoroalkenoic adds, derived from Michael addition of phenols to polyfluoro-2-alkynoic acids, undergo intramolecular Friedel-Crafts acylation to 2-polyfluoro-alkylchromones (94JFC25). 

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