Search

Thanks to a highly active catalyst, the scope of the (cyclopentadienone)iron complex-promoted 'hydrogen-borrowing' (HB) amination has been expanded to secondary alcohols, which had previously been reported to react only in the presence of large amounts of co-catalysts. A range of cyclic and acyclic secondary alcohols were reacted with aromatic and aliphatic amines giving fair to excellent yields of the substitution products. The catalyst was also able to promote the cyclization of diols bearing a secondary alcohol group with primary amines to generate saturated N-heterocycles. [ABSTRACT FROM AUTHOR]

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]

Abstract: Here we report the catalytic transfer hydrogenation (CTH) of non‐activated imines promoted by a Fe‐catalyst in the absence of Lewis acid co‐catalysts. Use of the (cyclopentadienone)iron complex 1, which is much more active than the classical ‘Knölker complex’ 2, allowed to reduce a number of N‐aryl and N‐alkyl imines in very good yields using iPrOH as hydrogen source. The reaction proceeds with relatively low catalyst loading (0.5–2 mol%) and, remarkably, its scope includes also ketimines, whose reduction with a Fe‐complex as the only catalyst has little precedents. Based on this methodology, we developed a one‐pot CTH protocol for the reductive amination of aldehydes/ketones, which provides access to secondary amines in high yield without the need to isolate imine intermediates. [ABSTRACT FROM AUTHOR]