Improving C=N Bond Reductions with (Cyclopentadienone)iron Complexes: Scope and Limitations.

Herein, we broaden the application scope of (cyclopentadienone)iron complexes 1 in C=N bond reduction. The catalytic scope of pre‐catalyst 1b, which is more active than the "Knölker complex" (1a) and other members of its family, has been expanded to the catalytic transfer hydrogenation (CTH) of a wider range of aldimines and ketimines, either pre‐isolated or generated in situ. The kinetics of 1b‐promoted CTH of ketimine S1 were assessed, showing a pseudo‐first order profile, with TOF = 6.07 h–1 at 50 % conversion. Moreover, the chiral complex 1c and its analog 1d were employed in the enantioselective reduction of ketimines and reductive amination of ketones, giving fair to good yields and moderate enantioselectivity. The catalytic transfer hydrogenation of imines and the reductive amination of carbonyl compounds have been thoroughly investigated with a cyclooctene‐derived (cyclopentadienone)iron pre‐catalyst. Additionally, enantioselective ketimine reduction with a chiral (cyclopentadienone)iron complex is reported here for the first time. [ABSTRACT FROM AUTHOR]