Reductive Amination of Ketonic Compounds Catalyzed by Cp*Ir(III) Complexes Bearing a Picolinamidato Ligand

Tanaka, Kouichi; Miki, Takashi; Murata, Kunihiko; Yamaguchi, Ayumi; Kayaki, Yoshihito; Kuwata, Shigeki; Ikariya, Takao; Watanabe, Minoru

doi:10.1021/acs.joc.9b01565

Cited by 42 publications

(29 citation statements)

References 87 publications

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“…Ir III -picolinamide complexes have been successfully applied as catalysts for av ariety of reactions, [29][30][31] includingw ater oxidation, [32] NAD + /NADH transformation, [32,33] and hydrogenation of CO 2 . [34] Recently,o ur group showedt hat they are also excellent catalysts for FA dehydrogenation.…”

Section: Introductionmentioning

confidence: 99%

Understanding the Deactivation Pathways of Iridium(III) Pyridine‐Carboxiamide Catalysts for Formic Acid Dehydrogenation

Rodriguez

Zaccaria

Tensi

et al. 2020

Chemistry A European J

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The degradation pathways of highly active [Cp*Ir(κ2‐N,N‐R‐pica)Cl] catalysts (pica=picolinamidate; 1 R=H, 2 R=Me) for formic acid (FA) dehydrogenation were investigated by NMR spectroscopy and DFT calculations. Under acidic conditions (1 equiv. of HNO3), 2 undergoes partial protonation of the amide moiety, inducing rapid κ2‐N,N to κ2‐N,O ligand isomerization. Consistently, DFT modeling on the simpler complex 1 showed that the κ2‐N,N key intermediate of FA dehydrogenation (INH), bearing a N‐protonated pica, can easily transform into the κ2‐N,O analogue (INH2; ΔG≠≈11 kcal mol−1, ΔG ≈−5 kcal mol−1). Intramolecular hydrogen liberation from INH2 is predicted to be rather prohibitive (ΔG≠≈26 kcal mol−1, ΔG≈23 kcal mol−1), indicating that FA dehydrogenation should involve mostly κ2‐N,N intermediates, at least at relatively high pH. Under FA dehydrogenation conditions, 2 was progressively consumed, and the vast majority of the Ir centers (58 %) were eventually found in the form of Cp*‐complexes with a pyridine‐amine ligand. This likely derived from hydrogenation of the pyridine‐carboxiamide via a hemiaminal intermediate, which could also be detected. Clear evidence for ligand hydrogenation being the main degradation pathway also for 1 was obtained, as further confirmed by spectroscopic and catalytic tests on the independently synthesized degradation product 1 c. DFT calculations confirmed that this side reaction is kinetically and thermodynamically accessible.

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Section: Introductionmentioning

confidence: 99%

Understanding the Deactivation Pathways of Iridium(III) Pyridine‐Carboxiamide Catalysts for Formic Acid Dehydrogenation

Rodriguez

Zaccaria

Tensi

et al. 2020

Chemistry A European J

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“…Soon after, a protocol of highly enantioselective Ru‐catalyzed DRA of aryl ketones was published, yet the limited scope of substrates, high degree of formamide side product formation, and a necessity to add ammonia hampered its broad application [3c] . Significant breakthrough was achieved by utilizing iridium half‐sandwich complexes [3d–h] . The performance of those catalysts bearing L‐X type ligands was similar and demonstrated a high substrate to catalyst molar ratio (1000–20 000) but demanded air‐free conditions.…”

Section: Figurementioning

confidence: 99%

Air Stable Iridium Catalysts for Direct Reductive Amination of Ketones

Polishchuk

Sklyaruk

Lebedev

et al. 2021

Chemistry A European J

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Half‐sandwich iridium complexes bearing bidentate urea‐phosphorus ligands were found to catalyze the direct reductive amination of aromatic and aliphatic ketones under mild conditions at 0.5 mol % loading with high selectivity towards primary amines. One of the complexes was found to be active in both the Leuckart–Wallach (NH4CO2H) type reaction as well as in the hydrogenative (H2/NH4AcO) reductive amination. The protocol with ammonium formate does not require an inert atmosphere, dry solvents, as well as additives and in contrast to previous reports takes place in hexafluoroisopropanol (HFIP) instead of methanol. Applying NH4CO2D or D2 resulted in a high degree of deuterium incorporation into the primary amine α‐position.

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“…One of the most powerful and robust methods for effective C-N bond formation of amines is the reductive amination of carbonyl compounds. [4,[18][19][20][21][22][23][24][25][26][27][28][29][30]. This transformation features compelling advantages, such as simple operating setups, mild reaction conditions, direct use of available substrates, and inexpensive reagents [31].…”

Section: Introductionmentioning

confidence: 99%

Base-Free Synthesis of Furfurylamines from Biomass Furans Using Ru Pincer Complexes

Pinheiro

Nielsen

2021

Catalysts

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Reductive Amination of Ketonic Compounds Catalyzed by Cp*Ir(III) Complexes Bearing a Picolinamidato Ligand

Cited by 42 publications

References 87 publications

Understanding the Deactivation Pathways of Iridium(III) Pyridine‐Carboxiamide Catalysts for Formic Acid Dehydrogenation

Understanding the Deactivation Pathways of Iridium(III) Pyridine‐Carboxiamide Catalysts for Formic Acid Dehydrogenation

Air Stable Iridium Catalysts for Direct Reductive Amination of Ketones

Base-Free Synthesis of Furfurylamines from Biomass Furans Using Ru Pincer Complexes

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