Ruthenium and Iridium Dipyridylamine Catalysts for the Efficient Synthesis of γ-Valerolactone by Transfer Hydrogenation of Levulinic Acid

Abstract

International audienceThe selective and efficient transfer hydrogenation of levulinic acid into γ-valerolactone was performed with new ruthenium and iridium catalysts bearing dipyridylamine (dpa) ligands. Reactions were performed in the presence of formic acid and triethylamine using catalyst loading as low as 0.05 mol % with a ruthenium complex (turnover number = 1980). Recyclability of a ruthenium catalyst was demonstrated by running 6 consecutive reactions in almost quantitative yields

Cyclopentanone Derivatives from 5‐Hydroxymethylfurfural via 1‐Hydroxyhexane‐2,5‐dione as Intermediate

“…We evaluated a series of air‐ and moisture‐stable iridium and ruthenium complexes (Figure ) that have not been previously used for the hydrogenation of HMF to HHD. The best results were obtained with the half‐sandwich [Cp*Ir(dpa)Cl]Cl (dpa=dipyridylamine) catalyst I (Table , entry 1), which is a known catalyst for water oxidation and the transfer hydrogenation of levulinic acid . Poor selectivities were observed with ruthenium complexes II , IV , and V (Figure and Table , entries 2, 4, and 5).…”

“…The best resultsw ere obtained with the half-sandwich [Cp*Ir(dpa)Cl]Cl (dpa = dipyridylamine) catalyst I ( Table 1, entry 1), which is ak nown catalyst for water oxidation [13] and the transfer hydrogenation of levulinic acid. [14] Poor selectivities were observed with ruthenium complexes II, IV,a nd V (Figure1 and Ta ble1,e ntries 2, 4, and 5). After fur- ther optimization,t he best resultsw ere obtained with I (0.5 mol %) with 10 bar H 2 at 120 8Ci nw ater and HHD was isolated in 69 %y ield ( Table 1, entry 1).…”

Base‐Free Dehydrogenation of Aqueous and Neat Formic Acid with Iridium(III) Cp*(dipyridylamine) Catalysts

“…Recently, our group has been investigating the reduction of levulinic acid into γ‐valerolactone by using ruthenium and iridium complexes bearing dipyridylamine ligands . This type of catalyst was earlier identified as efficient transfer hydrogenation catalysts of ketones in water .…”

“…Recently,o ur group has been investigating the reduction of levulinic acid into g-valerolactone by using ruthenium and iridium complexes bearing dipyridylamine ligands. [10] This type of catalystw as earlier identified as efficient transfer hydrogenation catalysts of ketones in water. [11] In particular, we demonstrated that the transfer hydrogenation of levulinic acid with formic acid was proceeding essentially by hydrogenation resulting from av ery fast initial formic acid dehydrogenation under base-free conditions.…”

“…We have thus studied some previously reported complexes and also prepared new complexesf eaturing (Figure1), in light of previous reports [13] and the studies on aqueous hydricity of late metal catalysts by Miller and co-workers. [14] The known Ir1-Ir4 and the new Ir5-Ir7 complexes were prepared according to ap reviously reported [10,12] procedure (see the Supporting Information). Crystals suitable for molecular structure determination by Xray diffraction were obtained for Ir5 ( Figure 2).…”