Site of protonation and BF3-complex formation of phenols in sulpholan

Abstract

The u.v. and n.m.r. spectra of a series of phenols dissolved in BF₃–sulpholan and HF–BF₃–sulpholan solutions are reported. BF₃-Complex formation always occurs on oxygen, but the adduct may tautomerise; for example, orcinol yields the BF₃-complex of 3-hydroxy-5-methylcyclohexa-2,5-dienone. In the HF–BF₃ solutions the relative importance of protonation and BF₃-complex formation could not be determined with certainty although the site of attack was clear.