Investigation of a Possible Solvent Cage Effect in the Reduction of 4‐Aminocyclohexanone by a Hydroxycyclopentadienyl Ruthenium Hydride

No solvent cage effect could be found in the reduction of 4‐aminocyclohexanone 3 by Shvo's hydroxycyclopentadienyl ruthenium hydride 2 . No preference was observed in the complex formation from trapping by aminoalcohol product 4 over external trapping by aminoketone 3 or by Shvo hydride 2 . A solvent cage effect has previously been proposed to support an outer‐sphere mechanism in the reduction of imines by 2 ; this was based on the observation that there was >90% preference for complexation of the newly formed amine over an external amine. Since alcohols form stronger hydrogen bonds than amines a larger cage effect would be expected in the present study. The lack of a cage effect in the present reduction suggests that the previous results from imine reduction require an additional explanation (other than a solvent cage effect).