Pandey, Pragati published the artcileA Proton-Responsive Annulated Mesoionic Carbene (MIC) Scaffold on Ir Complex for Proton/Hydride Shuttle: An Experimental and Computational Investigation on Reductive Amination of Aldehyde, Application of 2,7-Dimethyl-1,8-naphthyridine, the publication is Organometallics (2020), 39(21), 3849-3863, database is CAplus.
A Cp*Ir(III) complex (1) bearing a proton-responsive hydroxy unit on an annulated imidazo[1,2-a][1,8]naphthyridine based mesoionic carbene scaffold was synthesized by two different synthetic routes. The mol. structure of 1 revealed an anionic lactam form of the ligand. The acid-base equilibrium between the lactam-lactim tautomers on the ligand scaffold was examined by 1H NMR and UV-visible spectra. The pKa of the appendage -OH group in the lactim form of 1 was estimated to assess the proton transfer property of the catalyst. The catalytic efficacy of 1 for reductive amination of aldehyde was evaluated by using three different H sources: mol. H2, iPrOH/KOtBu combination, and HCOOH/Et3N (5:2) azeotropic mixture The HCOOH/Et3N (5:2) azeotropic mixture protocol is the best among the three different hydrogenation methods. Catalyst 1 hydrogenates imines chemoselectively over carbonyls under the reaction conditions. A range of aldehydes was reductively aminated to the corresponding secondary amines using the HCOOH/Et3N (5:2) azeotropic mixture Further, catalyst 1 showed high efficiency for the reduction of a wide variety of N-heterocyclic imine derivatives The lactam-lactim tautomerization of the ligand system is proposed for direct hydrogenation, whereas only the lactam form operates in the strongly basic medium (iPrOH/KOtBu). Under HCOOH/Et3N (5:2) conditions, the lactam scaffold is not protonated; rather, an outer-sphere hydride transfer from formate to the Ir is proposed, which is supported by 1H NMR and DFT calculations Finally, ligand-promoted hydride transfer from metal-hydride to the protonated imine affords the corresponding amine. A close agreement between the exptl. estimated and computed thermodn./kinetic parameters gives credence to the metal-ligand cooperative mechanism for the imine hydrogenation reaction using the HCOOH/Et3N (5:2) azeotropic mixture
Organometallics published new progress about 14903-78-7. 14903-78-7 belongs to naphthyridine, auxiliary class 6.6_Aromatics,Naphthyridines, name is 2,7-Dimethyl-1,8-naphthyridine, and the molecular formula is C10H10N2, Application of 2,7-Dimethyl-1,8-naphthyridine.
Referemce:
https://en.wikipedia.org/wiki/1,8-Naphthyridine,
1,8-Naphthyridine | C8H6N2 – PubChem