Anisole hydrolysis in high temperature water

Small organic radicals are ubiquitous intermediates in photocatalysis and are used in organic synthesis to install functional groups and to tune electronic properties and pharmacokinetic parameters of the final molecule. Development of new methods to generate small organic radicals with added functionality can further extend the utility of photocatalysis for synthetic needs. Herein, we present a method to generate dichloromethyl radicals from chloroform using a heterogeneous potassium poly(heptazine imide) (K-PHI) photocatalyst under visible light irradiation for C1-extension of the enone backbone. The method is applied on 15 enones, with γ,γ-dichloroketones yields of 18-89%. Due to negative zeta-potential (−40 mV) and small particle size (100 nm) K-PHI suspension is used in quasi-homogeneous flow-photoreactor increasing the productivity by 19 times compared to the batch approach. The resulting γ,γ-dichloroketones, are used as bifunctional building blocks to access valueadded organic compounds such as substituted furans and pyrroles.

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“…For example, cleavage of C-F bond in CF 3 -group is extremely demanding 16 . The same applies to C-O bond in the CH 3 O-group 17,18 .…”

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confidence: 97%

Dichloromethylation of enones by carbon nitride photocatalysis

et al. 2020

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“…Research on model compounds has demonstrated that water-tolerant Lewis acids (i.e., metal triflates) facilitate the cleavage of C−O bonds in hydrolysis of guaiacol, benzyl phenyl ether, diphenyl ether, and anisole in a hydrothermal media. 31,32 It is considered that the Lewis acid (Al(OTf) 3 ) used in this study was capable of catalyzing the cleavage of C−O and some C−C bonds in glucose and cellulose in hydrothermal media. Solid yields from the runs with Al(OTf) 3 were low in comparison to the noncatalytic run and the catalytic runs with NaOTf.…”

Section: Resultsmentioning

confidence: 99%

Effects of Acidic and Alkaline Metal Triflates on the Hydrothermal Carbonization of Glucose and Cellulose

2019

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The transformation of glucose and cellulose into carbon-rich solid materials was carried out in hydrothermal media at 200 °C for 48 h with and without the use of acidic (Al(OTf)3) and alkaline (NaOTf) catalysts. The effects of the catalyst type on the yield of hydrothermal carbons (HTCs) and their properties were investigated. The use of Al(OTf)3 led to a decrease in the yields of HTCs for both feedstocks. This result was reversed for the runs with NaOTf. Glucose-derived solid product without the use of a catalyst produced carbon spheres of a diameter between 500 and 600 nm. The use of a catalyst (regardless of whether Al(OTf)3 or NaOTf) produced larger particles. Scanning electron microscopy images of HTC from cellulose exhibited irregular morphology. Carbon spheres produced from cellulose without the use of a catalyst ranged between 200 nm and 2 μm. HTC products from cellulose with Al(OTf)3 yielded aggregated carbon spheres with a diameter ranging between 300 and 600 nm. The use of NaOTf inhibited the secondary char formation. Although a small number of carbon spheres were observed on the surface, the surface was mostly smooth, like raw cellulose. The final chemical structures of HTC products were further investigated using advanced 13C solid-state nuclear magnetic resonance (NMR). NMR spectra demonstrated that glucose was completely transformed into HTCs with and without a catalyst, because there were no peaks identified with carbon atoms of glucose. However, the peaks identified with carbon atoms of cellulose were observed in the non-catalytic and catalytic runs with NaOTf. Cellulose was completely transformed into HTCs with only Al(OTf)3.

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“…If that value applies to the ether linkages in lignin, then these bonds are much more stable to hydrolysis than the bonds linking the subunits of cellulose and other biological polymers in water at pH 7 in the absence of an enzyme, as indicated in Table . − Truly “uncatalyzed” ether hydrolysis has in fact been observed by several investigators, but only at temperatures (300–400 °C) approaching the critical point of water (374 °C). Assembling results from the literature for the hydrolysis of anisole in water, Rebacz and Savage have constructed an an Arrhenius plot that yields a Δ H ⧧ of 38 kcal/mol and an extrapolated rate constant of ∼10 –23 s –1 M –1 at 25 °C. That rate constant is several orders of magnitude slower than the rate constant estimated above for the H + -catalyzed reaction at pH 7, so that truly uncatalyzed hydrolysis is not expected to make a significant contribution to the rate of reaction in neutral solution except at temperatures above 300 °C.…”

Section: Resultsmentioning

confidence: 99%

Ether Hydrolysis, Ether Thiolysis, and the Catalytic Power of Etherases in the Disassembly of Lignin

Lewis

Wolfenden

2019

Biochemistry

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The recycling of much of the carbon in Nature depends on the breakdown of polymers in woody matter, notably cellulose (a polyacetal) and lignin (a polyether). Here, we show that equilibrium favors ether hydrolysis in water, although the rates of spontaneous hydrolysis of ethers are too slow to measure in neutral solution except at temperatures approaching the critical point of water. Circumventing that kinetic obstacle, glutathione-dependent etherases from white-rot fungi are known to employ the thiolate group of glutathione to attack guaiacyl ethers. Experiments at elevated temperatures indicate that thioglycolate attacks diethyl ether in water, in the absence of enzymes, with a rate constant of 6 × 10 −11 M −1 s −1 at 25 °C and that ether thiolysis is strongly favored thermodynamically, with a K eq value of 2.5 × 10 6 (ΔG = −8.7 kcal/mol). Compared with the rate of non-enzymatic thiolysis, the lignin-degrading etherases LigE and LigF produce 10 15 -fold rate enhancements, among the largest that have been observed for an enzyme acting on two substrates.I n the absence of microbial action, wood is remarkably durable, as exemplified by the survivalnearly intactof javelins manufactured ∼300000 years ago by Homo heidelbergensis. 1 Much of the fixed carbon on Earth is present in woody plants in the form of two linked polymers: cellulose (a polyacetal) and lignin (a polyether). Lignin disassembly is needed for the recycling of carbon in Nature and holds promise as a renewable source of valuable chemicals. 2 Recently, major efforts have been directed toward weakening lignin's structure, either by chemical methods or by the introduction of ester linkages by genetic modification. 3 At first glance, one might guess that the biological recycling of lignin, like the recycling of cellulose and other biopolymers, would proceed through the action of hydrolytic enzymes; however, only a single weakly active lignin hydrolase has been reported after many decades of effort, 3 and simple ethers have long been known to resist hydrolysis except in dilute HCl. 4 In the first part of this work, we performed experiments at elevated temperatures to determine equilibrium constants for the hydrolysis of simple alkyl ethers and alkyl-aryl ethers with linkages resembling those that hold lignin together (Scheme 1A). The results of these experiments, conducted in 1 M HCl to allow equilibrium to be established within a reasonable period of time, show that the hydrolysis of ethers is thermodynamically favored in dilute aqueous solution, with equilibrium constants (K 1 , eq 1) ranging from 4.5 M for dimethyl ether to 42 M for 2-methoxyphenol (guaiacol), an abundant constituent of lignin. Although hydrolysis is favored thermodynamically, these experiments showed that water

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Anisole hydrolysis in high temperature water

Cited by 12 publications

References 11 publications

Dichloromethylation of enones by carbon nitride photocatalysis

Dichloromethylation of enones by carbon nitride photocatalysis

Effects of Acidic and Alkaline Metal Triflates on the Hydrothermal Carbonization of Glucose and Cellulose

Ether Hydrolysis, Ether Thiolysis, and the Catalytic Power of Etherases in the Disassembly of Lignin

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