Ring inversion in 1,1-Dibenzylcyclohexanes

In a recent communication, the barrier to chair-chair interconversion in 1,1 -dimethyl-4,4-dibenzylcyclohexane (1a) was reported from studies of carbon and proton magnetic resonance spectroscopy to be at least 20 kcal/mol. This observation was surprising in terms of what is known about inversion barriers in cyclohexane and was rationalized in terms of hindered rotation of the benzyl groups