Dynopinacol (2-hydroxy-6-methyl-2,4,6-triphenylcyclohex-3-enyl phenyl ketone) and related compounds

Abstract

Structures have been assigned to derivatives of dypnopinacol (II)(2-hydroxy-6-methyl-2,4,6-triphenylcyclohex-3-enyl phenyl ketone) on the basis of spectral properties. Homodypnopinacol (V)(5-methyl-1,3,5,7-tetraphenylhept-2-ene-1,7-dione) re-forms dypnopinacol on mild treatment with base; prolonged action of base yields isodypnopinacolone (VII)(4-methyl-2,4,6-triphenylcyclohexa-2,6-dienyl phenyl ketone). Dehydration of dypnopinacol gives first α-dypnopinacolone (III)(6-methyl-2,4,6-triphenylcyclohexa-2,4-dienyl phenyl ketone) which is isomerised by acid to β-dypnopinacolone (IV)(6-methyl-2,4,6-triphenylcyclohexa-1,3-dienyl phenyl ketone). No stereochemical assignments are made except for a partial stereochemistry for the related condensation product (XIII)(2-hydroxy-2,4,6-triphenylcyclohex-3-enyl phenyl ketone) from dypnone (β-methylchalcone) and chalcone. A mechanism is suggested for the reaction of dypnone with sulphuric acid to give 2,4,6-triphenylpyrylium sulphate and isopropenylbenzene.