Pyridylidene-Mediated Dihydrogen Activation Coupled with Catalytic Imine Reduction

Johanna Auth; Jaroslav Padevet; Pablo Mauleón; Andreas Pfaltz

doi:10.1002/anie.201503233

Pyridylidene-Mediated Dihydrogen Activation Coupled with Catalytic Imine Reduction

Angew Chem Int Ed Engl. 2015 Aug 10;54(33):9542-5. doi: 10.1002/anie.201503233. Epub 2015 Jun 26.

Authors

Johanna Auth¹, Jaroslav Padevet¹, Pablo Mauleón², Andreas Pfaltz³

Affiliations

¹ Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel (Switzerland).
² Department of Organic Chemistry, Universidad Autónoma de Madrid c/Fco. Tomás y Valiente 7, Cantoblanco 28049, Madrid (Spain). pablo.mauleon@uam.es.
³ Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel (Switzerland). andreas.pfaltz@unibas.ch.

PMID: 26119973
DOI: 10.1002/anie.201503233

Abstract

In recent years, dihydrogen activation at non-metallic centers has received increasing attention. A system in which dihydrogen is trapped by a pyridylidene intermediate that is generated from a pyridinium salt and a base is now reported. The dihydropyridine formed in this process can act as reducing agent towards organic electrophiles. By coupling the hydrogen-activation step with subsequent hydride transfer from the dihydropyridine to an imine, a catalytic process was established. Treatment of the N-phenylimine of phenyl trifluoromethyl ketone with 5-20 mol% of N-mesityl-3,5-bis(2,6-dimethylphenyl)pyridinium triflate and 0.3-1.0 equivalents of LiN(SiMe3)2 under 50 bar of hydrogen gas resulted in high conversion into the corresponding amine.

Keywords: NADH analogues; catalytic hydrogenation; dihydrogen activation; pyridinium salts; pyridylidenes.