Applications of high potential quinones. Part IX. A stereoelectronic effect in the rates of quinone dehydrogenation of benzocycloalkenols

Abstract

The reactivity sequence tetralin-1-ol > indan-1-ol tetrahydrobenzocyclohepten-1-ol is observed in the dehydrogenation of these benzyl alcohols to the corresponding ketones by dichlorodicyanobenzoquinone. There is a linear relationship between the angle of inclination of the tertiary benzylic C–H bond to the plane of the aromatic ring and log k, reflecting the degree of σ–π overlap in the transition state for the oxidation. Factors underlying the preferred pseudo-axial conformation of the benzylic hydroxy-groups in these benzocycloalkenols are discussed.