What Is Thf Used For In Organic Chemistry

Tetrahydrofuran

Tetrahydrofuran (THF) is commonly used as solvent, reaction medium, and starting material for various syntheses in the chemic industry, for example, for preparing adhesives, special paints, coatings, fibers, in the extraction of specific active substances, for recrystallization of certain compounds or as starting material for diverse syntheses in a number of reactions.

From: Fundamental Modelling of Membrane Systems , 2018

Homometallic Alkoxides

D.C. Bradley , ... A. Singh , in Alkoxo and Aryloxo Derivatives of Metals, 2001

2.10.4 From Metal–Hydrogen Bond Cleavage Reactions (J-4)

The hydridic metal hydrides react with alcohols to yield hydride-alkoxides or binary alkoxides depending on the amounts of alcohols used.

Tetrahydrofuran soluble magnesium dialkoxides Mg(OR) _ii (where R = CPh₃ or CMePh_two) have been prepared ⁴⁰⁸ by the reactions of magnesium hydride or dimethyl magnesium with the respective alcohols:

(2.149) $\mathrm{Mg}{\mathrm{H}}_{\mathrm{two}}\left(\mathrm{or}\mathrm{Mg}{\mathrm{H}}_2\right)+\mathrm{ii}\mathrm{R}\mathrm{O}\mathrm{H}\to \mathrm{Mg}{\left(\mathrm{OR}\right)}_{\mathrm{two}}+{\mathrm{H}}_2\left(\mathrm{or}2\mathrm{C}{\mathrm{H}}_{\mathrm{iv}}\right)$

The hydrocarbon soluble alkoxides of even the heavier alkaline globe metals (Ba) are accessible ⁴⁷ according to Eq. (two.150):

(two.150) $\mathrm{Ba}{\mathrm{H}}_{\mathrm{two}}+2\mathrm{R}\mathrm{O}\mathrm{H}\to \mathrm{Ba}{\left(\mathrm{OR}\right)}_2+2{\mathrm{H}}_2\uparrow$

where R = CH(CF₃)₂ or C(CF₃)_iii.

In view of the importance of zinc hydride derivatives as catalysts for methanol product, ^{409 , 410} a number of alkoxozinc hydrides have been prepared by the reactions of ZnH₂ with a variety of alcohols:

(2.151) $2\mathrm{Z}\mathrm{n}{\mathrm{H}}_{\mathrm{ii}}+2\mathrm{R}\mathrm{O}\mathrm{H}\to 2\mathrm{H}\mathrm{Z}\mathrm{n}\left(\mathrm{OR}\right)+{\mathrm{H}}_{\mathrm{two}}$

where R = c-C_sixH₁₁, ⁴¹¹ CH_twoCH₂NMe₂, ⁴¹² and Bu^t. ⁴¹³

Aluminium hydride undergoes stepwise substitution ⁴¹⁴ by alcohols (Eq. two.152):

(2.152) $\mathrm{A}\mathrm{l}{\mathrm{H}}_{\mathrm{iii}}+x\mathrm{R}\mathrm{O}\mathrm{H}\to \mathrm{A}\mathrm{l}{\left(\mathrm{OR}\right)}_{\mathrm{ten}}{\mathrm{H}}_{3-x}+x/2{\mathrm{H}}_2$

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Five-Membered Heterocycles

Vishnu Ji Ram , ... Ramendra Pratap , in The Chemistry of Heterocycles, 2019

Applications

THF is used as a solvent in organic synthesis and chromatographic analysis, and is an intermediate of nylon-6,6. It is also used as an intermediate for synthetic pesticides, e.k., fenbutatin. It is directly used for synthetic fibers, synthetic resins, synthetic safety, as well every bit a solvent for many polymeric materials. It is widely used as surface coatings, anticorrosion coatings, and printing inks. In the pharmaceutical industry, THF is used for the synthesis of carbetapentane, rifamycin, progesterone, and some hormone drugs.

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Solvents and Supporting Electrolytes

Stephen Creager , in Handbook of Electrochemistry, 2007

3.v.half dozen Ethers, carbonates, lactone

Tetrahydrofuran (THF) and ane,two-dimethoxyethane (glyme) are the most usually used ether solvents in electrochemistry. They are very inert, especially toward reducing weather. They are adequately not-polar (low dielectric constants), which tin make dissolving electrolytes and achieving high conductivity in common salt solutions in these solvents hard. Organic carbonates such equally propylene carbonate (PC) and ethylene carbonate (EC), and lactones such as y-butyrolactone are particularly good choices for lithium salts such as LiPF ₆, LiTriflate, and LiTFSI, which are all widely used in lithium bombardment technology. They have not been widely used for other applications in electrochemistry just they should be well suited for such applications.

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Catalytic Processes of Lignocellulosic Feedstock Conversion for Product of Furfural, Levulinic Acrid, and Formic Acrid-Based Fuel Components

B. Kamm , ... Thou. Dautzenberg , in New and Time to come Developments in Catalysis, 2013

5.4.2 2-Methyl Tetrahydrofuran (MTHF)

2-Methyl tetrahydrofuran tin be obtained from GVL by catalytic hydrogenation and successive thermally- or acid-induced ring closure of the formed intermediate, one,4-pentanediol, as shown in Figure 5.eight. MTHF tin can also be obtained past a unmarried process that passes through the dissimilar reaction steps described past the use of a bimetallic goad and hydrogen directly from levulinic acid.

Effigy 5.viii. Catalytic hydrogenation of γ-Valerolactone and successive cyclization of 1,iv-pentanediol to 2-methyl tetrahydrofuran.

Yields of nearly xc% were achieved by the directly conversion of levulinic acid in the presence of a bimetallic goad on a carbon substrate of the composition Re(5%)/Pd(v%)/carbon with 100% conversion and selectivity of 89.5% [29].

Several attempts were made to obtain two-MTHF by liquid-stage hydrogenation from furfural. All of them delivered the product in low yields. However, catalytic hydrogenation by a continuous vapor-phase process was claimed to exist commercially feasible in a patent past Ahmed [1].

According to Lucas et al., 2-MTHF can be admixed to conventional gasoline up to 60% without requiring engine modification [72]. Compared to conventional fuels, ii-MTHF shows a reduced ozone building potential and reduced emissions (approximately i/3 less). Principal main drawbacks of MTHF include the high polarity that leads to swelling of elastomers in the tank and pumping equipment, the formation of peroxides, and loftier vapor pressure [52].

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Ring transformations past heterogeneous catalysis

Béla Török , ... Anne Kokel , in Heterogeneous Catalysis in Sustainable Synthesis, 2022

Tetrahydrofurans

Tetrahydrofurans and furans are important oxygen-containing heterocycles that often exhibit interesting properties for biological applications or applications in the corrective industry. They can hands be synthesized by acid-promoted intramolecular cyclization of unsaturated alcohols or aryloxyacetaldehyde acetals. ^{151, 152} Although traditional Brønsted acids are effective, ¹⁵³ they are considered to take a negative touch on the environment mainly due to the waste they generate, requiring neutralization. Solid acid catalysis, and the advantages often associated with their utilize, have been proved equally efficient for the synthesis of tetrahydrofurans or furans. Zeolites and silica-supported-catalysts have been used for this purpose. ^154–156 3 representative examples of such reactions are shown in Table seven.

Table 7. Heterogeneous catalytic synthesis of furans and tetrahydrofurans.

Entry	Starting materials	Catalyst/atmospheric condition	Product	Yield (%)	Ref.
i		H-BEA zeolite, CHthreeCH2NO2, 85°C, i.5   h		95	154
2		H-β zeolite, PhCFiii reflux, 0.5–10   h		71–95	155
3		AgNOiii-SiO2, CH2Cltwo, 20°C, iii   h		71–99	156

Brønsted and Lewis acrid sites-containing zeolites successfully catalyzed the conversion of diols and aryloxyacetaldehyde acetals to produce tetrahydrofurans and benzofurans, respectively in high yields. In both reactions, they exhibited good recyclability. ^{154, 155} A silica-supported argent catalyst led to the germination of trisubstituted furans from diols in nearly quantitative yields; the excellent purity of the products bypassed the need for purification steps. The recyclability of the catalyst was not investigated in the study. ¹⁵⁶ It must be noted that the solvents employed for all three reactions possess considerable toxicity and hazard.

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Applications of 2-Oxoaldehydes

Atul Kumar , ... Qazi Naveed Ahmed , in Chemistry of two-Oxoaldehydes and 2-Oxoacids, 2022

3.2.10 Synthesis of tetrahydrofuran

Tetrahydrofuran and dihydrofuran form the bones structural unit of many naturally occurring scaffolds like gambieric acrid A and ciguatoxin, ⁷⁵ goniocin, ⁷⁶ and some biologically agile molecules, for case, lasalocid A (X537A) ⁷⁷ (Fig. 3.31). Attributable to their importance in synthetic chemical science ⁷⁸ various strategies accept been launched for their synthesis ⁷⁹ based on cycloaddition and cyclization reactions.

Figure 3.31. Biologically active molecules containing tetrahydrofuran moiety.

two-Silyl methyl-substituted tetrahydrofurans (86a and 86b) were synthesized by Fuchibe et al. ⁸⁰ via [3+2] cycloaddition reactions of cyclopropyl methyl silanes 85a and AGs. Different reaction conditions were optimized past using dissimilar Lewis acids in different solvents and SnCl₄ in DCM was institute as best as far as the yields of the desired products are considered. Cis 86a and trans 86b isomers of the products are formed and the stereoselectivity of the products is dependent on the reaction temperature. Trans-isomer 86b was formed in major quantity when the reaction was carried out at 0°C and cis isomer 86a was formed at −78°C in major quantity (Fig. three.32).

Figure 3.32. Synthesis of two-silylmethyl substituted tetrahydrofurans.

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Molecular Weight Determination of Polyethylene Terephthalate

Shady Farah , ... Abraham J. Domb , in Poly(Ethylene Terephthalate) Based Blends, Composites and Nanocomposites, 2015

8.ii.vi.4 Mobile Stage for the Determination of Molecular Weight of PET by GPC

Tetrahydrofuran, chloroform, and toluene are most common solvents for the decision of molecular weights of common polymers such as polystyrene. Construction of a scale curve from the GPC organization using these solvents as mobile phase is straightforward, due to polystyrene standard ease solubility [40]. However, PET is an unmanageable polymer for the determination of molecular weights past GPC. Initially, m-cresol was used as mobile stage for the elution of PET using GPC; due to the viscous nature of this solvent, higher cavalcade temperature (125°C) must exist used, which leads to polymer deposition. Other solvents used in GPC for the PET are a mixture of nitrobenzene and tetrachloroethane at room temperature; degradation of PET was non observed for several months [twoscore]. Still, difficulties in preparing the samples were observed. HFIP and pentafluorophenol too every bit their mixtures were used every bit the mobile stage in GPC for PET [41]. HFIP is capable of dissolving the PET at room temperature and is bachelor commercially. The just disadvantage is that polystyrene standards are not soluble with this solvent. To overcome this drawback a mixture of chloroform and HFIP has been used as a mobile phase [42]. Recently our group studied 14 different PET cobweb samples using the HFIP:chloroform, 2:98 v/v, as mobile phase for the determination of their molecular weights [27].

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Five-membered Rings with One Heteroatom Together with Their Benzo and Other Carbocyclic-fused Derivatives

Zhuliang Zhong , Xiao-Shui Peng , in Comprehensive Heterocyclic Chemical science IV, 2022

3.07.four.two.one [3   +   2] Cyclizations

The tetrahydrofuran containing bicyclo [two.2.ane] skeleton was accomplished via an intermolecular Prins double cyclization in the total synthesis of natural production (+)-chabranol. ³⁸⁷ In the formal synthesis of (−)-platensimycin, a benzoxa[3.2.one]octane was constructed from a benzylic oxacarbenium cation intermediate. ³⁸⁸ The synthesis of the cage-like core of (−)-platensimycin that contains a tetrahydrofuran ring was achieved by utilizing a carbonyl ylide cycloaddition approach. ³⁸⁹ The oxabicyclo[3.two.1]octane was obtained through the chiral Rh(II) circuitous-catalyzed enantioselective carbonyl ylide cycloaddition of 2-diazo-3,6-diketoester with a vinyl ether dipolarophile en route to englerin A. ³⁹⁰

The total syntheses of natural products hainanolidol and harringtonolide were realized featuring two [3,three]-sigmatropic rearrangements, and an oxidopyrylium-based [5   +   ii] cycloaddition to construct the tetracyclic carbon skeleton and the tetrahydrofuran unit of measurement (Scheme 244). ³⁹¹

Scheme 244.

In an asymmetric synthesis of (+)-polyanthellin A, the crucial tetrahydrofuran intermediate 622 was assembled via a related MADNTf₂-catalyzed formal [3   +   two] cycloaddition of a donor–acceptor cyclopropane 620 and a β-silyloxy aldehyde 621 (Scheme 245). ³⁹²

Scheme 245.

As shown in Scheme 246, a cation-olefin cascade cyclization was developed to construct furan-fused 6,iii,5-tricyclic arrangement 624 under an acrid promotion with a loftier stereochemical fidelity from the electrophilic middle of the epoxide to the cyclopropane product. ³⁹³

Scheme 246.

A diversity of chiral furo[3,4-b]indoles of blazon 627 were obtained through an asymmetric [iii   +   2] cycloaddition of indoles 626 and epoxides 625 with loftier enantioselectivities and diastereoselectivities. The reaction is displayed in Scheme 247. ³⁹⁴

Scheme 247.

A diastereoselective synthesis of cis-ii,5-disubstituted tetrahydrofurans via a Lewis acid catalyzed [3   +   2] cycloaddition of donor–acceptor cyclopropanes and aldehydes was reported. ³⁹⁵ A like reaction catalyzed by Pd(0) was also realized. ³⁹⁶ Diethyl ii,5-diaryl-four-benzoyltetrahydrofuran-iii,three-dicarboxylates of type 630 were produced via an AlCl₃-catalyzed diastereoselective [3   +   ii] cycloaddition reaction of diethyl trans-ii,three-disubstituted cyclopropane-1,ane-dicarboxylates 628 (Scheme 248). ³⁹⁷ The application of cis-2,3-disubstituted cyclopropane 1,1-diesters to [three   +   2]-annulations with aldehydes under the promotion of AlCl₃ resulted in the formation of the desired polysubstituted tetrahydrofuran products. ³⁹⁸ A [three   +   2] annulation of the geraniol-derived cyclopropane-fused lactone with aromatic aldehydes led to tetrahydrofuran derivatives in a loftier yield and an endo-stereoselectivity. ³⁹⁹ Aminotetrahydrofurans could exist synthesized through a novel Atomic number 26(3)-catalyzed [3   +   2] annulation of aminocyclopropanes with aldehydes in an splendid 2,v-cis selectivity. ⁴⁰⁰

Scheme 248.

An efficient preparation of the enantioenriched tetrahydrofuran 634 through a dynamic kinetic asymmetric transformation of the donor–acceptor cyclopropane 631 via an asymmetric [3   +   ii] cycloaddition with aldehydes 632 is outlined in Scheme 249. ⁴⁰¹ The ruthenium-catalyzed [3   +   2] cycloaddition of ethynylcyclopropanes, bearing two carboxy groups at the homopropargylic position, with aldehydes and aldimines was developed for the synthesis of the respective 2-ethynyltetrahydrofurans. ⁴⁰²

Scheme 249.

Under a cooperative catalysis of photo and Lewis acids, a tandem isomerization/intramolecular [iii   +   2] cross cycloaddition of cyclopropane 1,ane-diesters 635 with α,β-unsaturated ketones/aldehydes was successfully developed to class carbocycle-based bridged oxa-bicyclo[north.2.1] (northward = 4–6) skeletons of blazon 636 with a tetrahydrofuran unit (Scheme 250). ⁴⁰³

Scheme 250.

Every bit depicted in Scheme 251, a novel i-pot asymmetric synthesis of ii- and 2,three-disubstituted tetrahydrofurans of type 639 from aliphatic and effluvious aldehydes 637 using Ipc-derived chiral allyl, crotyl and alkoxyallylborane reagents 638 was achieved via an allylboration-hydroboration-iodination-cyclization reaction sequence. ⁴⁰⁴

Scheme 251.

A palladium-catalyzed [3   +   2] cycloaddition between trimethylenemethane 640 and aldehydes 641 using a novel phosphoramidite ligand resulted in the formation of chiral methylenetetrahydrofurans of type 642 (Scheme 252). ⁴⁰⁵ The novel palladium-catalyzed [3   +   2] cycloaddition of trimethylenemethane with ketones provided an access to the highly enantioenriched tetrahydrofurans bearing a tetrasubstituted stereocenter with a C1-symmetric phosphoramidite. ⁴⁰⁶

Scheme 252.

An efficient synthesis of 3,4-dimethylidene tetrahydrofuran 645 through a Prins-type cyclization of hydroxy(allenylmethyl)silane 643 with aldehyde 644 is described in Scheme 253. ⁴⁰⁷ SnBr₄-promoted oxonium-Prins cyclization was reported to class ii,3-disubstituted tetrahydrofurans. ⁴⁰⁸

Scheme 253.

The novel goad-dependent chemoselective cycloaddition or dienylation reaction between bis-substituted allenoates 647 and trifluoromethyl ketones 646 chemoselectively afforded CF₃-substituted tetrahydrofurans of type 648 and dienyl tertiary alcohols with commercially bachelor simple phosphine catalysts in good yields and Due east selectivity (Scheme 254). ⁴⁰⁹

Scheme 254.

Equally illustrated in Scheme 255, a phosphine-catalyzed β,γ-Umpolung domino reaction of allenic esters 431 with dienones 649 underwent a highly stereoselective oxy-Michael/Rauhut–Currier sequence to produce highly functionalized 3-methylenetetrahydrofurans of type 650. ⁴¹⁰

Scheme 255.

An disproportionate Diels–Alder cycloaddition of masked ortho-benzoquinones with alkenols by using sugars as chiral auxiliaries afforded the optically pure bicyclo[2.2.ii]oct-5-en-two-ones. ⁴¹¹ A new PRCC (polar-radical-crossover cycloaddition) reaction catalyzed by an organic photoredox system to synthesize highly substituted tetrahydrofurans of type 654 from readily bachelor allylic alcohols 651 and oxidizable alkenes 652 was demonstrated (Scheme 256). ⁴¹²

Scheme 256.

Based on a rare case of an asymmetric one,6-improver to linear ii,iv-dienals 656 proceeding with high δ-site and stereoselectivity, a novel aminocatalytic vinylogous pour reaction was adult to yield valuable tetrahydrofuran spirooxindole derivatives of type 657 equally shown in Scheme 257. ⁴¹³

Scheme 257.

The commencement platinum-catalyzed enantioselective preparation of 8-oxabicyclo[iii.two.one]octane derivatives via an disproportionate [3   +   two]-cycloaddition reaction of a Pt-containing carbonyl ylide, generated from alk-iv-yn-1-ones, was described. ⁴¹⁴ A Pt(II)-catalyzed reaction of γ,δ-ynones with alkenes led to the formation of 8-oxabicyclo[three.2.1]octane frameworks. ⁴¹⁵ As displayed in Scheme 258, an efficient Au-catalyzed oxidative domino reaction of enyne aldehydes and ketones 658 afforded tetracyclic ketoethers and heteroaromatic analogs of type 659 by using pyridine North-oxides equally external oxidants. ⁴¹⁶ Complex tetrahydrofurans were as well synthesized via a stereocontrolled Pt-catalyzed [four   +   two]-cycloaddition/annulation of enynals with allylic alcohols. ⁴¹⁷

Scheme 258.

An asymmetric oxa-Michael/Michael cascade reaction of π-quinols 660 and α,β-unsaturated aldehydes 644 provided an access to 4 contiguous stereocenters of the hindered tetrahydrofuran of type 661 with expert diastereoselection. The reaction is outlined in Scheme 259. ⁴¹⁸

Scheme 259.

The novel indole [5   +   2] cycloaddition involving an oxidopyrylium ylide resulted in the construction of oxa-cyclohepta[b]indoles of type 663 with a high functional-grouping tolerance and a unique endo selectivity under mild reaction atmospheric condition (Scheme 260). ⁴¹⁹

Scheme 260.

As depicted in Scheme 261, a blazon Two intramolecular oxidopyrylium-mediated [v   +   2] cycloaddition reaction led to the efficient and diastereoselective germination of various tetrahydrofurans of type 666 with a high functional-group tolerance and a unique endo selectivity. ⁴²⁰

Scheme 261.

By using a palladium goad generated in situ from [Pd₂(dba)₃]·CHCl_three and a phosphoramidite ligand, a mild and efficient method for the decarboxylative cycloaddition of vinylethylene carbonates 667 with activated Michael acceptors 668 was adult to afford multifunctionalized tetrahydrofurans of type 669 bearing face-to-face tertiary and vicinal quaternary stereocenters (Scheme 262). ⁴²¹

Scheme 262.

As described in Scheme 263, a silver-catalyzed reaction of aldehydes 670 with alkenes underwent a tandem one,3-dipolar cycloaddition/cyclopropanation to synthesize a series of polycyclic compounds of type 671 with a tetrahydrofuran moiety. ⁴²²

Scheme 263.

In the presence of dinuclear zinc-AzePhenol complex, α-hydroxyacetophenone 672 and β,γ-unsaturated α-keto esters 673 underwent an enantioselective domino Michael/hemiketalization reaction to construct multiple-substituted chiral tetrahydrofurans of type 675 (Scheme 264). ⁴²³

Scheme 264.

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Progress in Heterocyclic Chemical science

Steven J. Collier , ... Naga K. Modukuru , in Progress in Heterocyclic Chemistry, 2009

one.5.ii Tetrahydrofuran Derivatives

Chiral tetrahydrofurans are readily attainable using resolutions < 94BMC387; 93JCS(P1)313> and desymmetrizations <01ASC527; 01MI355; 00JOC847> with instance products of each given below. Intermediate 26 was used to prepare (-) podophyllotoxin and picrodophyllin <00JOC847>. Bicyclic hydroxyfurans have been prepared via lipase mediated acylative desymmetrization of meso diols <03TL2225>. Chiral furanones have been prepared past lipase mediated lactonisations. For example, meso-hydroxydiester 27 can undergo a porcine pancreatic lipase catalyzed desymmetrization via lactonization giving (S)-furanone 28 in high optical yield. The (R)-isomer could be obtained using Pseudomonas fluorescens lipase, although ee's were lower <89JOC4263; 95MI87>. Handling of 3,four-epoxytetrahydrofuran with an epoxide hydrolase tin give the corresponding (threeR,fourR)-diol <04JA11156>. Epoxide hydrolases have besides been employed in an elegant enzyme-triggered enantioconvergent cascade reaction. Thus racemic ii,iii-disubstituted cis-2-chloroalkyl epoxides 29 can be hydrolyzed enantioconvergently using resting cells of Rhodococcus sp. or Rhodococcus ruber. Ane enantiomer is cleaved with retention of stereochemistry, the other with inversion, providing a single, stereo-defined chlorodiol intermediate 30, which spontaneously cyclizes to yield chiral 3-hydroxytetrahydrofurans 31 as sole products in adept yields and reasonable ee's <01TA41; 01EJO4537>.

Enzymatic ketone reductions have also been shown to provide chiral dihydro- and tetrahydrofuran-iii-ols in high ee from the corresponding ketones, with either enantiomer attainable through option of an advisable variant <07ACR1412>. Enzymatic reductions of ketones begetting pendant ester groups to chiral alcohols tin result in cyclization of the intermediate hydroxyester to give chiral butyrolactones. Enzymes from the yeasts Mucor rouxii <04TA3763> or Pichia etchellsi <01TA1039> gave fantabulous yields and ee's.

Oxidations accept too proved to be valuable and efficient approaches to chiral tetrahydrofuran derivatives. For example, HLADH (equus caballus liver alcohol dehydrogenase) catalyzes the oxidation of meso 1,four-diols 32 to give enantiomerically pure furanones 33 bearing fused rings of varying sizes on multigram scale <82JA4659>. Cyclobutene-fused furanones take been prepared using the same approach <99TA403>. Chiral dihydrobenzofuran diol 34 was synthesized from benzofuran using toluene dioxygenase <96CC2361>.

There are many examples of the synthesis of stereochemically defined ω-butyrolactones, using the enzymatic Baeyer-Villiger oxidation of substituted cyclobutanones with a range of isolated enzymes or whole jail cell processes. The products of such reactions play a key part in the synthesis of many types of natural products and therapeutic agents (specially those bearing substituents at the iii-position) <93JOC2725>. High stereoselectivities and expert yields can be obtained using the mucus Cunninghamella echinulata in whole cell processes <00JMOC209; 98JMOC219> and the same or like substrates can exist also prepared from isolated Baeyer-Villiger monooxygenases (BVMO), such as cyclohexanone monooxygenases (CHMO), cyclopentanone monooxygenases (CPMO), or iv-hydroxyacetophenone monooxygenases (HAPMO) <07ASC1436>. Bacteria expressing a mutant CHMO (F432S) were tested confronting a range of ketones in a 24-well microplate, in some cases giving products with high conversion and good ee <06OL1221>. An interesting variant of this approach involves the Baeyer-Villiger oxidation of 4-hydroxycyclohexanone, to requite (South)-four-hydroxycaprolactone 34 which spontaneously rearranges to requite an (S)-butyrolactone derivative 35 <04AG(I)4075>. The product could exist obtained in loftier yield and good stereoselectivity after screening and directed development.

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Monolithic Materials

David Sýkora , František Švec , in Periodical of Chromatography Library, 2003

20.vii.4 Polybutadienes

Since THF–methanol did not perform well in the separation of polybutadienes in HPLC mode, dichloromethane was used as the solvent in combination with methanol (precipitant) to achieve the molecular weight-dependent separation [39]. The optimized v step gradient profile one time again affords a linear scale curve for all five polybutadiene standards that were available. The separation of these polybutadienes is shown in Fig. 20.15. The run time was almost vi   min at a period rate of 1   mL/min. However, doubling the flow rate to ii   mL/min and halving the gradient time enabled the separation to be achieved inside 3   min. A further acceleration was possible by running the gradient within only 1.25   min. Although the resolution of peaks ii and 3 is slightly lower in this rapid run, the complete separation of the mixture of polybutadiene standards is achieved within one   min.

Fig. 20.xv. Event of slope time and flow rate on the separation of a mixture of five polybutadiene standards using a 50   ×   4.6   mm i.d. monolithic poly(styrene-co-divinylbenzene) cavalcade. Separation weather condition: non-linear gradients of dichloromethane in methanol (a) overall slope time v.v   min consisting of 0–75% in 3   min, 75–79% in 0.v   min, 79–81% in 0.five   min, 81–84% in one   min, and 84–100% in 0.5   min; (b) overall gradient time 2.75   min consisting of 0–75% in 1.5   min, 75–79% in 0.25   min, 79–81% in 0.25   min, 81–84% in 0.5   min, and 84–100% in 0.25   min, (c) overall gradient time ane.38   min consisting of 0–75% in 0.75   min, 75–79% in 0.xiii   min, 79–81% in 0.12   min, 81–84% in 0.25   min, and 84–100% in 0.thirteen   min); menses rate ane (a) and 2   mL/min (b,c); sample volume 10   μL; overall sample concentration: 25   mg/mL (each standard 5   mg/mL) in THF; ELSD detection. Molecular weights of polymer standards 520 (ane), 2,820 (ii), half dozen,000 (iii), 24,800 (4), and 215,800 (5).

(Reprinted from ref. [39]. Copyright 2000 Wiley)

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What Is Thf Used For In Organic Chemistry,

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