Bimolecular formation of radicals by hydrogen transfer, 9. Uncatalyzed transfer hydrogenation of α‐methylstyrene by 9,10‐dihydroacridine and N‐methyl‐9,10‐dihydroacridine

Hydrogen is transferred from acridane (1c) and N‐methylacridane (1d) to α‐methyl‐styrene (2) in a bimolecular uncatalyzed reaction at 260–300°C. On the basis of the activation parameters (for 1c: ΔH≠ = 29.0 kcal/mol, ΔS≠ = −23.5 e.u. in triglyme) the kinetic isotope effect (kH/kD = 2.0, in triglyme at 300°C) as well as the small solvent effects and from the observation of an EPR signal of N‐methylhydroacridyl radicals a three‐step radical mechanism is prosposed which is initiated by a retrodisproportionation between 1 and 2.