Ruthenium/1,1′‐Bis(diphenylphosphino)ferrocene‐Catalysed Oppenauer Oxidation of Alcohols and Lactonisation of α,ω‐Diols using Methyl Isobutyl Ketone as Oxidant

Abstract

A number of ruthenium catalysts, made in situ from [RuA C H T U N G T R E N N U N G (p-cymene)Cl 2 ] 2 and various monodentate and bidentate phosphorus ligands were screened in the double Oppenauer oxidation of 1,6-hexanediol to caprolactone using methyl isobutyl ketone as oxidant and potassium carbonate as base. The catalyst based on 1,1'-bis(diphenylphosphinyl)ferrocene gave this lactone in excellent yield. The same catalyst was evaluated for the oxidation of other diols to their lactones, of primary alcohols to the corresponding aldehydes and of secondary alcohols to the ketones under the same reaction conditions. The products were obtained in moderate to excellent yields.

Direct Transformation of HMF into 2,5‐Diformylfuran and 2,5‐Dihydroxymethylfuran without an External Oxidant or Reductant

“…Although the HMF conversion was slightly improved to 13.4 % in methyl isobutyl ketone (MIBK), the DFF/DHMF molar ratio (1.63) was still much higher than 1.0 (Table , entry 3). This high DFF/DHMF molar ratio indicates that intermolecular hydrogen transfer between the keto group of MIBK and the hydroxyl group of HMF simultaneously occurs in the MIBK system, similar to the case of DMSO and DMF, except for the disproportionation of HMF (Scheme S1) . This intermolecular hydrogen transfer between HMF and MIBK leads to the formation of more DFF than DHMF, which could also be verified by the presence of methyl isobutyl carbinol (MIBC) among the products (Figure S1 C).…”

“…This high DFF/ DHMF molar ratio indicatest hat intermolecular hydrogen transfer between the keto group of MIBK and the hydroxyl group of HMF simultaneously occurs in the MIBK system, similar to the case of DMSO and DMF,e xcept for the disproportionation of HMF (Scheme S1). [14] This intermolecular hydrogen transfer between HMF and MIBK leads to the formation of more DFF than DHMF,w hich could also be verifiedb yt he presenceo fm ethyl isobutyl carbinol (MIBC) among the products (Figure S1 C). The presence of acyl (DMSO and DMF) and keto groups (MIBK) in the three solvents mentioned above can interferew itht he MPVO reactionb etween HMF molecules and therebyi nfluence the HMF conversion and DFF/DHMFm olar ratio.…”

Catalytic Conversion of Renewable Resources into Bulk and Fine Chemicals

“…Next, we examined the dehydrogenation of 1,6‐hexanediol to caprolactone 23. In fact, this is a dehydrogenation, followed by the formation of the cyclic hemiacetal, which is dehydrogenated again (Scheme ).…”

“…To maximize the selectivity, we tested a range of bidentate phosphines in combination with the ruthenium catalyst precursor (Table ). This led to the finding that use of 1,1'‐bis(diphenylphosphino)ferrocene (dppf) results in complete conversion and full selectivity to the desired caprolactone 23…”

Acceptorless dehydrogenative lactonization of diols by Pt-loaded SnO2 catalysts

“…A number of homogeneous and heterogeneous catalytic systems have been reported to be effective for the oxidative lactonization of diols by oxidants, such as carbonyl compounds, [9][10][11][12][13][14] oxygen [15][16][17][18][19] and hydrogen peroxide. Dehydrogenative 1-8 and oxidative 9-20 lactonizations of diols are potentially useful methods for the synthesis of lactones.…”