Iron-catalyzed cross etherification of alcohols to form unsymmetrical benzyl ethers

Zhang, Lingjuan; González-de-Castro, Ángela; Chen, Changjun; Li, Faju; Xi, Siqi; Xu, Lijin; Xiao, Jianliang

doi:10.1016/j.mcat.2016.12.014

Cited by 19 publications

(18 citation statements)

References 53 publications

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“…Homogeneously catalytic systems including Brønsted acids (e.g., H 2 SO 4 , H 3 PO 4 , and H 3 PO 2 ), Lewis acids [e.g., BuSnCl 3 , CuBr 2 , and Fe(OTf) 3 ], and metalbased complex catalysts (e.g., Ru/P/Al) have been widely applied in catalyzing dehydrative cyclization of diols to access cyclic ethers (5,(7)(8)(9). However, they generally suffer from corrosion, pollution, and difficulty in separation, thus limiting their practical applications (10)(11)(12)(13)(14)(15). Heterogeneous catalysts with high performances and stability, including solid-acid catalysts (e.g., -Al 2 O 3 , H-ZSM-5, H-Y, and H-ZSM-22) and solid-metal complexes (e.g., NHC-Ir), have also been intensively applied in the dehydrative cyclization of diols, which require high temperature (e.g., 200° to 400°C), leading to the formation of by-products (e.g., hydrocarbons and coke) and deactivation of catalysts (11,(16)(17)(18)(19).…”

Section: Introductionmentioning

confidence: 99%

Hydrogen-bond donor and acceptor cooperative catalysis strategy for cyclic dehydration of diols to access O-heterocycles

et al. 2021

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Dehydrative cyclization of diols to O-heterocycles is attractive, but acid and/or metal-based catalysts are generally required. Here, we present a hydrogen-bond donor and acceptor cooperative catalysis strategy for the synthesis of O-heterocycles from diols in ionic liquids [ILs; e.g., 1-hydroxyethyl-3-methyl imidazolium trifluoromethanesulfonate ([HO-EtMIm][OTf])] under metal-free, acid-free, and mild conditions. [HO-EtMIm][OTf] is tolerant to a wide diol scope, shows performance even better than H2SO4, and affords a series of O-heterocycles including tetrahydrofurans, tetrahydropyrans, morpholines, dioxanes, and thioxane in high yields. Mechanism investigation indicates that the IL cation and anion serve as hydrogen-bond donor and acceptor, respectively, to activate the C─O and O─H bonds of alcohol via hydrogen bonds, which synergistically catalyze dehydrative cyclization of diols to O-heterocycles. Notably, the products could be spontaneously separated after reaction because of their immiscibility with the IL, and the IL could be recycled. This green strategy has great potential for application in industry.

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Section: Introductionmentioning

confidence: 99%

Hydrogen-bond donor and acceptor cooperative catalysis strategy for cyclic dehydration of diols to access O-heterocycles

et al. 2021

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“…The Gunanathan group used ammonium chloride (5 mol%) as an additive to tune the selectivity towards ethers in the Fe(OTf) 3 (5 mol%) catalyzed dehydrative coupling of 1‐phenyl ethanol at 0 °C in dichloromethane [15f] . In a very similar work, Xu and Xiao had demonstrated the utility of Fe(OTf) 2 in combination with 2,6‐ bis (4,5‐diphenyl‐4,5‐dihydro‐1H‐imidazol‐2‐yl)pyridine (1 mol%) in accomplishing the cross etherification of alcohols to form unsymmetrical benzyl ethers at 80 °C in 1,2‐dichloroethane [15g] . Kim and co‐workers reported the FeCl 3 (3 mol%) catalyzed cross etherification of 2‐diphenyloxy‐1‐methylpyridine with several alcohols to obtain diphenylmethyl ethers at 70 °C in DCE [15j] .…”

Section: Introductionmentioning

confidence: 99%

Pincer‐Ruthenium Catalyzed Oxygen Mediated Dehydrative Etherification of Alcohols and Ortho‐Alkylation of Phenols

2022

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In the current report, a dehydration strategy has been formulated for the selective etherification of secondary alcohols catalyzed by NNN pincer-ruthenium(II) carbonyl complexes based on bis(imino)pyridine ligands in the presence of molecular oxygen under solvent-free and base-free conditions at 140 °C. Under these conditions, very high yields (up to 92%, ca. 6133 TON) of the corresponding ethers are obtained at a very low catalyst loading (ca. 0.015 mol%). Mechanistic studies provide key evidence for the various events that occur during the catalytic cycle. While iodometric titration gives quantitative proof for the liberation of hydrogen peroxide in catalytic amounts and hence confirms the role of oxygen as a co-catalyst, DFT, HRMS, IR and 13 C NMR analysis are indicative of the non-labile nature of the ancillary CO ligand. On the other hand, DFT, NMR and HRMS studies reveal the hemi-labile nature of the pincer-ligand in the presence of oxygen. EPR analysis provide conclusive evidence for generation of Ru(III) species via single electron transfer (SET) from O 2 . Apparently the Ru(III) species ( Ph2 NN)RuCl 2 (CO)(OH) is the resting-state of the etherification reaction and several of its derivatives have been detected by HRMS analysis. The pincer-ruthenium catalyzed etherification of 1-phenyl ethanol has been successfully extended not only to various aromatic secondary alcohols but also to the cross-etherification and/or oalkylation of 1-phenyl ethanols with a variety of phenols. Readily available oxygen and tiny amounts (0.015 mol%) of pincer-Ru catalyst are the only requirement for this atom-economical and environmentally benign dehydrative etherification reaction which apparently has not been reported thus far.

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“…16 However, most of these reactions are moisture sensitive which makes them inconvenient for operating and difficult to deal with. Therefore, methods with other catalysts, such as Cu( ii ), 17 Fe( iii ), 18 Ru, 19 Pd( ii ) 20 and organocatalysts, 21 have been employed to overcome these shortcomings.…”

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confidence: 99%

Iridium-catalyzed reductive etherification of α,β-unsaturated ketones and aldehydes with alcohols

et al. 2022

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Iron-catalyzed cross etherification of alcohols to form unsymmetrical benzyl ethers

Cited by 19 publications

References 53 publications

Hydrogen-bond donor and acceptor cooperative catalysis strategy for cyclic dehydration of diols to access O-heterocycles

Hydrogen-bond donor and acceptor cooperative catalysis strategy for cyclic dehydration of diols to access O-heterocycles

Pincer‐Ruthenium Catalyzed Oxygen Mediated Dehydrative Etherification of Alcohols and Ortho‐Alkylation of Phenols

Iridium-catalyzed reductive etherification of α,β-unsaturated ketones and aldehydes with alcohols

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