Low-temperature functionalisation of alkanes and cycloalkanes by 'classical' and 'non-classical' (superacidic) Friedel–Crafts complexes

The results of studies on direct functionalisation of activated alkanes and cycloalkanes under the action of 'classical' Friedel–Crafts complexes (viz. equimolar complexes of acyl halides with aluminium halides) and related systems containing smaller or somewhat larger amounts of aluminium halide are surveyed. The studies carried out during the last decade on functionalisation of saturated hydrocarbons devoid of tertiary carbon atoms, by aprotic organic superacids RCOX^.2AlCl₃ are summarised. Reactions of alkanes with acylium cations in superacidic media are considered. The published data on the structure of complexes RCOX ^. AlCl₃ and RCOX ^. 2AlCl₃ and on the nature of the active complexes in the reactions of arenes with acylium cations and with complexes RCOX ^.AlCl₃ in both acidic and organic media as well as in the reactions of alkanes with acylium salts in protic superacids and with superacidic complexes RCOX ^.2AlCl₃ in aprotic solvents are analysed. The prospects for the synthesis of organic compounds from alkanes and cycloalkanes under the action of complexes of acyl halides with aluminium halides are outlined. The bibliography includes 128 references.