Transfer Hydrogenation of Aldehydes and Ketones with Isopropanol under Neutral Conditions Catalyzed by a Metal–Ligand Bifunctional Catalyst [Cp*Ir(2,2′-bpyO)(H₂O)]

Abstract

A Cp*Ir complex bearing a functional bipyridonate ligand [Cp*Ir(2,2'-bpyO)(HO)] was found to be a highly efficient and general catalyst for transfer hydrogenation of aldehydes and chemoselective transfer hydrogenation of unsaturated aldehydes with isopropanol under neutral conditions. It was noteworthy that many readily reducible or labile functional groups such as nitro, cyano, ester, and halide did not undergo any change under the reaction conditions. Furthermore, this catalytic system exhibited high activity for transfer hydrogenation of ketones with isopropanol. Notably, this research exhibited new potential of metal-ligand bifunctional catalysts for transfer hydrogenation.

Transfer Hydrogenation of Carbonyl Groups, Imines andN‐Heterocycles Catalyzed by Simple, Bipyridine‐Based MnIComplexes

“…The alkene C=C double bond remained unreacted under these conditions (entry 16), and in the case of diketone 7 l, the corresponding dialcohol 8 l was obtained as a major product (entry 12). Aliphatic ketones ( Table 2, entries [14][15][16][17][18] were also effectively hydrogenated to give the corresponding alcohol products in good yields.…”

“…Bioinspired Ir complexes with dihydroxy‐substituted bipyridine and bipyrimidine were also developed that act as efficient catalysts for reversible hydrogenation of CO 2 and dehydrogenation of formic acid . Recently, Li and co‐workers showed that Ir complex with 6,6′‐dihydroxy‐2,2′‐bipyridine is an active catalyst of TH of aldehydes and ketones, while unsubstituted and mono‐hydroxy‐substituted bipyridine analogs show no activity or much lower product yields …”

“…[16] Recently, Li and co-workers showed that Ir complex with 6,6'-dihydroxy-2,2'bipyridine is an active catalyst of TH of aldehydes and ketones, while unsubstituted and mono-hydroxy-substituted bipyridine analogs show no activity or much lower product yields. [17] In this study, we expand the reactivity of the Mn complexes with simple substituted bipyridine ligands to transfer hydrogenation of ketones, aldehydes and imines. We found that while the most active and stable catalysts were dihydroxysubstituted complexes, complexes with other electron-rich bipyridines not containing OH groups also showed some catalytic activity, indicating that the effect of the proton shuttle groups in the ligand second coordination sphere is less pronounced for transfer hydrogenation compared to CO 2 hydrogenation by the same complexes.…”

Reduction of Aldehydes with Formic acid in Ethanol using Immobilized Iridium Nanoparticles on a Triazine‐phosphanimine Polymeric Organic Support

“…isopropanol, 82 C, N 2 , 6 hr 93 465 [43] 6 (1.0) HCOONa/HCO 2 H, H 2 O, pH = 2.5, 80 C, 12 hr 96 96 [44] 7 (0.5) glucose, H 2 O, Na 2 CO 3 , 100 C, 20 h 86 172 [45] 8 Au-SiO 2 (1.0) 2,4,6-trimethylpyridine, iPrOH, H 2 (6 bar), 100 C, 24 hr 100 100 [46] 9 Ni-nanoparticles (10.0) HCOONH 4 , THF, 25 C, N 2 , 1.5 hr 85 8.5 [47] 10 Pd-nanoparticles (1.0) H 2 , H 2 O, rt, 6 hr 90 90 [48] stirred for 12 hr at 80 C. Then the reaction mixture was filtered and the filtrate was concentrated under vacuum to yield the crude product. The crude product was purified by column chromatography, eluting with hexane/EtOAc, to afford the desired product.…”

Iridium-Catalyzed Transfer Hydrogenation of Ketones and Aldehydes Using Glucose as a Sustainable Hydrogen Donor

“…The most well-known of these would be the Meerwein-Ponndorf-Verley (MPV)-type reduction using 2-propanol as a hydrogen donor. Although an aluminum catalyst is typically used in MPV-type reductions [5,6], many highly efficient systems using transition metal catalysts have been reported [7][8][9][10][11][12]. However, MPV-type reduction depends on the equilibrium between alcohols and carbonyl compounds; therefore, a large excess of 2-propanol as a hydrogen donor must be used to obtain an alcohol in high yield.…”