Manganese-Catalyzed Hydrogenation of Amides and Polyurethanes: Is Catalyst Inhibition an Additional Barrier to the Efficient Hydrogenation of Amides and Their Derivatives?

Abstract

The hydrogenation of amides and other less electrophilic carbonyl derivatives with an N−C�O functionality requires significant improvements in scope and catalytic activity to be a genuinely useful reaction in industry. Here, we report the results of a study that examined whether such reactions are further disadvantaged by nitrogen-containing compounds such as aliphatic amines acting as inhibitors on the catalysts. In this case, an enantiomerically pure manganese catalyst previously established to be efficient in the hydrogenation of ketones, N-aryl-imines, and esters was used as a prototype of a manganese catalyst. This was accomplished by doping a model ester hydrogenation with various nitrogen-containing compounds and monitoring progress. Following from this, a protocol for the catalytic hydrogenation of amides and polyurethanes is described, including the catalytic hydrogenation of an axially chiral amide that resulted in low levels of kinetic resolution. The hypothesis of nitrogen-containing compounds acting as an inhibitor in the catalytic hydrogenation process has also been rationalized by using spectroscopy (high-pressure infrared (IR), nuclear magnetic resonance (NMR)) and mass spectrometry studies.

Chiral P,N,N‐Ligands for Asymmetric Hydrogenation

“…The development of more efficient catalysts for enantioselective hydrogenation of olefins and imines is still an unmet need. An example of hydrogenation of amides with Mn/P,N,N-ligands catalyst was reported recently by Clarke [103] et al The axially chiral amide was obtained by the amide hydrogenolysis with kinetic resolution. Although the ee value was low, it was an unusual and novel type of asymmetric hydrogenation and would be a worthwhile goal for future development.…”