| 1. |
- Abu-Omar, Mahdi M., et al.
(författare)
-
Guidelines for performing lignin-first biorefining
- 2021
-
Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 14:1, s. 262-292
-
Forskningsöversikt (refereegranskat)abstract
- The valorisation of the plant biopolymer lignin is now recognised as essential to enabling the economic viability of the lignocellulosic biorefining industry. In this context, the lignin-first biorefining approach, in which lignin valorisation is considered in the design phase, has demonstrated the fullest utilisation of lignocellulose. We define lignin-first methods as active stabilisation approaches that solubilise lignin from native lignocellulosic biomass while avoiding condensation reactions that lead to more recalcitrant lignin polymers. This active stabilisation can be accomplished by solvolysis and catalytic conversion of reactive intermediates to stable products or by protection-group chemistry of lignin oligomers or reactive monomers. Across the growing body of literature in this field, there are disparate approaches to report and analyse the results from lignin-first approaches, thus making quantitative comparisons between studies challenging. To that end, we present herein a set of guidelines for analysing critical data from lignin-first approaches, including feedstock analysis and process parameters, with the ambition of uniting the lignin-first research community around a common set of reportable metrics. These guidelines comprise standards and best practices or minimum requirements for feedstock analysis, stressing reporting of the fractionation efficiency, product yields, solvent mass balances, catalyst efficiency, and the requirements for additional reagents such as reducing, oxidising, or capping agents. Our goal is to establish best practices for the research community at large primarily to enable direct comparisons between studies from different laboratories. The use of these guidelines will be helpful for the newcomers to this field and pivotal for further progress in this exciting research area.
|
|
| 2. |
- Bartling, Andrew W., et al.
(författare)
-
Techno-economic analysis and life cycle assessment of a biorefinery utilizing reductive catalytic fractionation
- 2021
-
Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 14:8, s. 4147-4168
-
Tidskriftsartikel (refereegranskat)abstract
- Reductive catalytic fractionation (RCF) is a promising approach to fractionate lignocellulose and convert lignin to a narrow product slate. To guide research towards commercialization, cost and sustainability must be considered. Here we report a techno-economic analysis (TEA), life cycle assessment (LCA), and air emission analysis of the RCF process, wherein biomass carbohydrates are converted to ethanol and the RCF oil is the lignin-derived product. The base-case process, using a feedstock supply of 2000 dry metric tons per day, methanol as a solvent, and H-2 gas as a hydrogen source, predicts a minimum selling price (MSP) of crude RCF oil of $1.13 per kg when ethanol is sold at $2.50 per gallon of gasoline-equivalent ($0.66 per liter of gasoline-equivalent). We estimate that the RCF process accounts for 57% of biorefinery installed capital costs, 77% of positive life cycle global warming potential (GWP) (excluding carbon uptake), and 43% of positive cumulative energy demand (CED). Of $563.7 MM total installed capital costs, the RCF area accounts for $323.5 MM, driven by high-pressure reactors. Solvent recycle and water removal via distillation incur a process heat demand equivalent to 73% of the biomass energy content, and accounts for 35% of total operating costs. In contrast, H-2 cost and catalyst recycle are relatively minor contributors to operating costs and environmental impacts. In the carbohydrate-rich pulps, polysaccharide retention is predicted not to substantially affect the RCF oil MSP. Analysis of cases using different solvents and hemicellulose as an in situ hydrogen donor reveals that reducing reactor pressure and the use of low vapor pressure solvents could reduce both capital costs and environmental impacts. Processes that reduce the energy demand for solvent separation also improve GWP, CED, and air emissions. Additionally, despite requiring natural gas imports, converting lignin as a biorefinery co-product could significantly reduce non-greenhouse gas air emissions compared to burning lignin. Overall, this study suggests that research should prioritize ways to lower RCF operating pressure to reduce capital expenses associated with high-pressure reactors, minimize solvent loading to reduce reactor size and energy required for solvent recovery, implement condensed-phase separations for solvent recovery, and utilize the entirety of RCF oil to maximize value-added product revenues.
|
|
| 3. |
- Argyropoulos, Dimitris D. S., et al.
(författare)
-
Kraft Lignin: A Valuable, Sustainable Resource, Opportunities and Challenges
- 2023
-
Ingår i: ChemSusChem. - : John Wiley and Sons Inc. - 1864-5631 .- 1864-564X. ; 16:23
-
Forskningsöversikt (refereegranskat)abstract
- Kraft lignin, a by-product from the production of pulp, is currently incinerated in the recovery boiler during the chemical recovery cycle, generating valuable bioenergy and recycling inorganic chemicals to the pulping process operation. Removing lignin from the black liquor or its gasification lowers the recovery boiler load enabling increased pulp production. During the past ten years, lignin separation technologies have emerged and the interest of the research community to valorize this underutilized resource has been invigorated. The aim of this Review is to give (1) a dedicated overview of the kraft process with a focus on the lignin, (2) an overview of applications that are being developed, and (3) a techno-economic and life cycle asseeements of value chains from black liquor to different products. Overall, it is anticipated that this effort will inspire further work for developing and using kraft lignin as a commodity raw material for new applications undeniably promoting pivotal global sustainability concerns.
|
|
| 4. |
- Casey, Charles P., et al.
(författare)
-
Quantitative Determination of the Regioselectivity of Nucleophilic Addition to η3-Propargyl Rhenium Complexes and Direct Observation of an Equilibrium between η3-Propargyl Rhenium Complexes and Rhenacyclobutenes.
- 2009
-
Ingår i: Organometallics. - : American Chemical Society (ACS). - 0276-7333 .- 1520-6041. ; 28:1, s. 123-131
-
Tidskriftsartikel (refereegranskat)abstract
- PMe3 adds selectively to the central C of the η3-propargyl complex [C5Me5(CO)2Re(η3-CH2C≡CCMe3)][BF4] (1-t-Bu) to form the metallacyclobutene [C5Me5(CO)2Re(CH2C(PMe3):CCMe3)][BF4] (7). The rate of rearrangement of the metallacyclobutene 7 to η2-alkyne complex [C5Me5(CO)2Re(η2-Me3PCH2C≡CCMe3)][BF4] (8) is independent of phosphine concn., consistent with a dissociative mechanism proceeding via η3-propargyl complex 1-t-Bu. The rate of this rearrangement is 480 times slower than the rate of exchange of PMe3 with the labeled metallacyclobutene 7-d9. This rate ratio provides an indirect measurement of the regioselectivity for addn. of PMe3 to the central C of η3-propargyl complex 1-t-Bu to give 7 compared to addn. to a terminal C to give 8. The addn. of PPh3 to 1-t-Bu gives the metallacyclobutene [C5Me5(CO)2Re(CH2C(PPh3):CCMe3)][BF4] (11). Low-temp. 1H NMR spectra provide evidence for an equil. between metallacyclobutene 11 and η3-propargyl complex 1-t-Bu (Keq ≈ 44 M-1 at -46° and ΔG°(0°) = -1.2 ± 0.2 kcal mol-1). The crystal and mol. structures of [C5Me5(CO)2Re[η2-(Ar2PCH2CH2PPh2)CH2C≡CCMe3]][BF4]·2CH2Cl2 (Ar = 3,5-(CF3)2C6H3) and [C5Me5(CO)2Re(η2-Me3PCH2C≡CCMe3)]Cl·H2O were detd. by x-ray crystallog. [on SciFinder(R)]
|
|
| 5. |
- Lebedeva, Daria, 1994-, et al.
(författare)
-
Synthesis of Cyclobutane-Based Sustainable Aviation Fuel from Prehydrolysis Liquors
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Maximizing products of high value and minimizing incineration of side-streams is key to realize future biorefineries. In current textile production from forestry, hemicellulose is removed by prehydrolysis before delignification. The resulting prehydrolysis liquor is incinerated in the recovery boiler at low efficiency. This additional burden on the limiting recovery boiler reduces the pulp production. In this study, we demonstrate that prehydrolysis liquor can be upgraded, in 5 steps, to yield aviation fuels. Prehydrolysis liquors were dehydrated to furfural by zeolite catalysis. Furfural was selecitvely reduced to furfuryl alcohol by homogeneous catalysis. Rhenium-catalyzed Achmatowicz rearrangement gave a C5 intermediate susceptable to self [2+2] cycloaddition to give the C10 oxygenated precursor. By using a combination of Ru/C and zeolites, full hydrodeoxygenation was achieved. The resulting hydrocarbons, containing a strained four-membered ring, are preferred aviation fuel components. This is an important step to show that aviation fuels can be produced sustainably from existing industrial side-streams.
|
|
| 6. |
- Lebedeva, Daria, 1994-
(författare)
-
Valorization of low-value lignocellulosic side-streams
- 2024
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of novel pathways for valorizing low-value streams from pulp, forest, and agricultural industries is crucial for realizing a circular bioeconomy and addressing the needs of both platform chemicals and fuels. Utilizing hemicellulose and lignin as biomass-derived feedstocks facilitates the production of sustainable liquid hydrocarbons, with catalytic hydrodeoxygenation being a key process. In the utilization of hemicellulose for the synthesis of liquid hydrocarbons, the approach involves recovering hemicellulosic sugars from wood and transforming them into furfural, which undergoes catalytic hydrodeoxygenation using a noble metal/zeolite tandem catalyst. This results in the production of pentane as the primary product. The process also generates C7–C10 hydrocarbons through bimolecular condensation of oxygenated intermediates alongside the formation of aromatic structures. Another approach involves a three-step transformation of furfural, including furanic ring rearrangement and [2+2] cycloaddition, which produces a C10 oxygenated precursor with a 4-membered ring. Catalytic hydrodeoxygenation of this precursor results in the formation of cyclobutane-containing hydrocarbons for sustainable aviation fuel applications.In the utilization of lignin for the synthesis of liquid hydrocarbons, the approach involves lignin isolation from biomass and its direct catalytic hydrodeoxygenation into valuable platform chemicals and fuels. Guaiacol serves as a lignin model compound, facilitating optimization of the hydrotreatment process and giving insights into the distribution of the products. The hydrodeoxygenation of two different lignins, isolated from biomass by organosolv and soda pulping, yields bio-oils rich in hydrocarbons and suitable for transportation fuel applications.
|
|
| 7. |
- Subbotina, Elena, et al.
(författare)
-
Oxidative cleavage of C-C bonds in lignin
- 2021
-
Ingår i: Nature Chemistry. - : Springer Science and Business Media LLC. - 1755-4330 .- 1755-4349. ; 13, s. 1118-1125
-
Tidskriftsartikel (refereegranskat)abstract
- Lignin is an aromatic polymer that constitutes up to 30 wt% of woody biomass and is considered the largest source of renewable aromatics. Valorization of the lignin stream is pivotal for making biorefining sustainable. Monomeric units in lignin are bound via C–O and C–C bonds. The majority of existing methods for the production of valuable compounds from lignin are based on the depolymerization of lignin via cleavage of relatively labile C–O bonds within lignin structure, which leads to yields of only 36–40 wt%. The remaining fraction (60 wt%) is a complex mixture of high-molecular-weight lignin, generally left unvalorized. Here we present a method to produce additional valuable monomers from the high-molecular-weight lignin fraction through oxidative C–C bond cleavage. This oxidation reaction proceeds with a high selectivity to give 2,6-dimethoxybenzoquinone (DMBQ) from high-molecular-weight lignin in 18 wt% yield, thus increasing the yield of monomers by 32%. This is an important step to make biorefining competitive with petroleum-based refineries.
|
|
| 8. |
- Watile, Rahul A., et al.
(författare)
-
Intramolecular substitutions of secondary and tertiary alcohols with chirality transfer by an iron(III) catalyst
- 2019
-
Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 10:1
-
Tidskriftsartikel (refereegranskat)abstract
- Optically pure alcohols are abundant in nature and attractive as feedstock for organic synthesis but challenging for further transformation using atom efficient and sustainable methodologies, particularly when there is a desire to conserve the chirality. Usually, substitution of the OH group of stereogenic alcohols with conservation of chirality requires derivatization as part of a complex, stoichiometric procedure. We herein demonstrate that a simple, inexpensive, and environmentally benign iron(III) catalyst promotes the direct intramolecular substitution of enantiomerically enriched secondary and tertiary alcohols with O-, N-, and S-centered nucleophiles to generate valuable 5-membered, 6-membered and aryl-fused 6-membered heterocyclic compounds with chirality transfer and water as the only byproduct. The power of the methodology is demonstrated in the total synthesis of (+)-lentiginosine from D-glucose where iron-catalysis is used in a key step. Adoption of this methodology will contribute towards the transition to sustainable and bio-based processes in the pharmaceutical and agrochemical industries. © 2019, The Author(s).
|
|
| 9. |
- Adler, Anneli, et al.
(författare)
-
Lignin-first biorefining of Nordic poplar to produce cellulose fibers could displace cotton production on agricultural lands
- 2022
-
Ingår i: Joule. - : Elsevier BV. - 2542-4351. ; 6:8, s. 1845-1858
-
Tidskriftsartikel (refereegranskat)abstract
- Here, we show that lignin-first biorefining of poplar can enable the production of dissolving cellulose pulp that can produce regenerated cellulose, which could substitute cotton. These results in turn indicate that agricultural land dedicated to cotton could be reclaimed for food production by extending poplar plantations to produce textile fibers. Based on climate-adapted poplar clones capable of growth on marginal lands in the Nordic region, we estimate an environmentally sustainable annual biomass production of ∼11 tonnes/ha. At scale, lignin-first biorefining of this poplar could annually generate 2.4 tonnes/ha of dissolving pulp for textiles and 1.1 m3 biofuels. Life cycle assessment indicates that, relative to cotton production, this approach could substantially reduce water consumption and identifies certain areas for further improvement. Overall, this work highlights a new value chain to reduce the environmental footprint of textiles, chemicals, and biofuels while enabling land reclamation and water savings from cotton back to food production.
|
|
| 10. |
|
|
| 11. |
- Akkarasamiyo, Sunisa, et al.
(författare)
-
Intermolecular Stereospecific Substitution of Underivatized Enantioenriched Secondary Alcohols by Organocatalysis
- 2019
-
Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 58:50, s. 17908-17910
-
Tidskriftsartikel (refereegranskat)abstract
- The stereospecific substitution of non-derivatized and non-allylic enantioenriched alcohols with only water as a by-product would enable the use of readily available alcohols as substrates for green and sustainable transformations. However, the poor leaving group ability of the OH group has hampered the development of such a process. Denton and co-workers recently described the use of (2-hydroxybenzyl)diphenylphosphine oxide as a catalyst of a redox-neutral and zero-waste-generating Mitsunobu reaction. This innovative process constitutes the first intermolecular stereospecific substitution of non-allylic alcohols, and might find industrial applications.
|
|
| 12. |
- Akkarasamiyo, Sunisa, et al.
(författare)
-
Nickel-Catalyzed Stereospecific Deoxygenation of trans- Aromatic Epoxides to (Z)-Alkenes : An Efficient Route to Access (Z)-Cinnamic Acid Derivatives
- 2024
-
Ingår i: Asian journal of organic chemistry, ISSN 2193-5807; EISSN 2193-5815. - 2193-5807 .- 2193-5815. ; 13:5, s. e202400009-
-
Tidskriftsartikel (refereegranskat)abstract
- A stereospecific deoxygenation of trans-epoxy cinnamic acid derivatives to access (Z)-cinnamamides, (Z)-cinnamyl alcohol and (Z)-cinnamyl amines using a catalytic system based on nickel triflate and triphenylphosphine has been developed. The desired products were obtained in good to excellent yield (up to 92 % isolated yield) and excellent stereospecificity (Z : E ratio up to>99 : 1). The transformation has a broad functional group tolerance including amides, amines, alcohols and esters. The power of the methodology was demonstrated in the key step of the total synthesis of biologically active natural product, N-cis-feruloyl tyramine from readily available trans-ferulic acid. A reaction mechanism involving activation of epoxide via coordination of the oxygen atom and the neighboring O- or N-atoms to the nickel catalyst and formation of Ph3P-carbon bond is proposed. This method is important for synthesis of highly desirable functionalized (Z)-alkenes from readily available (E)-alkenes. © 2024 Wiley-VCH GmbH.
|
|
| 13. |
- Akkarasamiyo, Sunisa, et al.
(författare)
-
Nickel-Catalyzed Suzuki-Miyaura Cross-Coupling Reaction of Naphthyl and Quinolyl Alcohols with Boronic Acids
- 2019
-
Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 21:12, s. 4782-4787
-
Tidskriftsartikel (refereegranskat)abstract
- A nickel-catalyzed C(sp(3))-C(sp(2)) Suzuki cross-coupling of arylboronic acids and (hetero)naphthyl alcohols has been developed. A Ni(dppp) Cl-2 complex showed the highest efficiency and broadest substrate scope. High functional group tolerance has been achieved where 35 compounds could be generated in good to excellent yields, including both primary and secondary benzylic alcohols. Mechanistic studies using multiple NMR techniques as well as ESI-HRMS showed that the C-O cleavage is facilitated by an activation of the benzylic alcohol through formation of a boronic ester intermediate.
|
|
| 14. |
- Akkarasamiyo, Sunisa, et al.
(författare)
-
Synthesis of (Z)-Cinnamate Esters by Nickel-Catalyzed Stereoinvertive Deoxygenation of trans-3-Arylglycidates
- 2022
-
Ingår i: Synlett. - : Georg Thieme Verlag KG. - 0936-5214 .- 1437-2096. ; 33:14, s. 1353-1356
-
Tidskriftsartikel (refereegranskat)abstract
- We report a stereoinvertive deoxygenation of trans-3-arylglycidates as an alternative route to access thermodynamically less stable (Z)-cinnamate esters by using nickel triflate and triphenylphosphine. Broad functional-group tolerance was observed, with trans-3-arylglycidates containing methyl, methoxy, halo, or nitro groups affording the corresponding (Z)-cinnamate esters in high yields and with moderate to high E/Z ratios.
|
|
| 15. |
- Akkarasamiyo, Sunisa, et al.
(författare)
-
Transition-Metal-Catalyzed Suzuki-Miyaura-Type Cross-Coupling Reactions of π-Activated Alcohols
- 2020
-
Ingår i: Synthesis (Stuttgart). - : Georg Thieme Verlag KG. - 0039-7881 .- 1437-210X. ; 52:5, s. 645-659
-
Forskningsöversikt (refereegranskat)abstract
- The Suzuki-Miyaura reaction is one of the most powerful tools for the formation of carbon-carbon bonds in organic synthesis. The utilization of alcohols in this powerful reaction is a challenging task. This short review covers progress in the transition-metal-catalyzed Suzuki--Miyaura-type cross-coupling reaction of pi-activated alcohol, such as aryl, benzylic, allylic, propargylic and allenic alcohols, between 2000 and June 2019.
|
|
| 16. |
- Akkarasamiyo, Sunisa, et al.
(författare)
-
Tsuji-Trost Reaction of Non-Derivatized Allylic Alcohols
- 2018
-
Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 24:14, s. 3488-3498
-
Tidskriftsartikel (refereegranskat)abstract
- Palladium-catalyzed allylic substitution of non-derivatized enantioenriched allylic alcohols with a variety of uncharged N-, S-, C- and O-centered nucleophiles using a bidentate BiPhePhos ligand is described. A remarkable effect of the counter ion (X) of the XPd[kappa(2)-BiPhePhos][kappa(3)-C3H5] was observed. When ClPd[kappa(2)-BiPhePhos][eta(3)-C3H5] (complexI) was used as catalyst, non-reproducible results were obtained. Study of the complex by X-ray crystallography, (PNMR)-P-31 spectroscopy, and ESI-MS showed that a decomposition occurred where one of the phosphite ligands was oxidized to the corresponding phosphate, generating ClPd[kappa(1)-BiPhePhosphite-phosphate][eta(3)-C3H5] species (complexII). When the chloride was exchanged to the weaker coordinating OTf- counter ion the more stable Pd[kappa(2)-BiPhePhos][eta(3)-C3H5](+)+[OTf] (-) (complexIII) was formed. ComplexIII performed better and gave higher enantiospecificities in the substitution reactions. ComplexIII was evaluated in Tsuji-Trost reactions of stereogenic non-derivatized allylic alcohols. The desired products were obtained in good to excellent yields (71-98%) and enantiospecificities (73-99%) for both inter- and intramolecular substitution reactions with only water generated as a by-product. The methodology was applied to key steps in total synthesis of (S)-cuspareine and (+)-lentiginosine. A reaction mechanism involving a palladium hydride as a key intermediate in the activation of the hydroxyl group is proposed in the overall transformation.
|
|
| 17. |
- Biswas, Srijit, et al.
(författare)
-
Atom-Efficient Gold(I)-Chloride-Catalyzed Synthesis of alpha-Sulfenylated Carbonyl Compounds from Propargylic Alcohols and Aryl Thiols : Substrate Scope and Experimental and Theoretical Mechanistic Investigation
- 2013
-
Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 19:52, s. 17939-17950
-
Tidskriftsartikel (refereegranskat)abstract
- Gold(I)-chloride-catalyzed synthesis of -sulfenylated carbonyl compounds from propargylic alcohols and aryl thiols showed a wide substrate scope with respect to both propargylic alcohols and aryl thiols. Primary and secondary aromatic propargylic alcohols generated -sulfenylated aldehydes and ketones in 60-97% yield. Secondary aliphatic propargylic alcohols generated -sulfenylated ketones in yields of 47-71%. Different gold sources and ligand effects were studied, and it was shown that gold(I) chloride gave the highest product yields. Experimental and theoretical studies demonstrated that the reaction proceeds in two separate steps. A sulfenylated allylic alcohol, generated by initial regioselective attack of the aryl thiol on the triple bond of the propargylic alcohol, was isolated, evaluated, and found to be an intermediate in the reaction. Deuterium labeling experiments showed that the protons from the propargylic alcohol and aryl thiol were transferred to the 3-position, and that the hydride from the alcohol was transferred to the 2-position of the product. Density functional theory (DFT) calculations showed that the observed regioselectivity of the aryl thiol attack towards the 2-position of propargylic alcohol was determined by a low-energy, five-membered cyclic protodeauration transition state instead of the strained, four-membered cyclic transition state found for attack at the 3-position. Experimental data and DFT calculations supported that the second step of the reaction is initiated by protonation of the double bond of the sulfenylated allylic alcohol with a proton donor coordinated to gold(I) chloride. This in turn allows for a 1,2-hydride shift, generating the final product of the reaction.
|
|
| 18. |
|
|
| 19. |
- Biswas, Srijit, et al.
(författare)
-
Tandem Pd/Au-Catalyzed Route to alpha-Sulfenylated Carbonyl Compounds from Terminal Propargylic Alcohols and Thiols
- 2014
-
Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 20:8, s. 2159-2163
-
Tidskriftsartikel (refereegranskat)abstract
- An efficient and highly atom-economical tandem Pd/Au-catalyzed route to -sulfenylated carbonyl compounds from terminal propargylic alcohols and thiols has been developed. This one-step procedure has a wide substrate scope with respect to substituents at the -position of the alcohol. Both aromatic and aliphatic thiols generated the -sulfenylated carbonyl products in good to excellent yields. A mechanism is proposed in which the reaction proceeds through a Pd-catalyzed regioselective hydrothiolation at the terminal triple bond of the propargyl alcohol followed by an Au-catalyzed 1,2-hydride migration.
|
|
| 20. |
- Bunrit, Anon, et al.
(författare)
-
A General Route to beta-Substituted Pyrroles by Transition-Metal Catalysis
- 2016
-
Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 81:4, s. 1450-1460
-
Tidskriftsartikel (refereegranskat)abstract
- An atom-efficient route to pyrroles substituted in the beta-position has been achieved in four high yielding steps by a combination of Pd, Ru, and Fe catalysis with only water and ethene as side-products. The reaction is general and gives pyrroles substituted in the beta-position with linear and branched alkyl, benzyl, or aryl groups in overall good yields. The synthetic route includes a Pd-catalyzed monoallylation step of amines with substituted allylic alcohols that proceeds to yield the monoallylated products in moderate to excellent yields. In a second step, unsymmetrical diallylated aromatic amines are generated from the reaction of a second allylic alcohol with high selectivity in moderate to good yields by control of the reaction temperature. Ru-catalyzed ring-closing metathesis performed on the diallylated aromatic amines yields the pyrrolines substituted in the beta-position in excellent yields. By addition of ferric chloride to the reaction mixture, a selective aromatization to yield the corresponding pyrroles substituted in the beta-position was achieved. A reaction mechanism involving a palladium hydride, generated from insertion of palladium to O-H of an allyl alcohol, that is responsible for the C-O bond cleavage to generate the pi-allyl intermediate is proposed.
|
|
| 21. |
- Bunrit, Anon, et al.
(författare)
-
Brønsted Acid-Catalyzed Intramolecular Nucleophilic Substitution of the Hydroxyl Group in Stereogenic Alcohols with Chirality Transfer
- 2015
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 137:14, s. 4646-4649
-
Tidskriftsartikel (refereegranskat)abstract
- The hydroxyl group of enantioenriched benzyl, propargyl, allyl, and alkyl alcohols has been intramolecularly displaced by uncharged O-, N-, and S-centered nucleophiles to yield enantioenriched tetrahydrofuran, pyrrolidine, and tetrahydrothiophene derivatives with phosphinic acid catalysis. The five-membered heterocyclic products are generated in good to excellent yields, with high degree of chirality transfer, and water as the only side-product. Racemization experiments show that phosphinic acid does not promote S(N)1 reactivity. Density functional theory calculations corroborate a reaction pathway where the phosphinic acid operates as a bifunctional catalyst in the intramolecular substitution reaction. In this mechanism, the acidic proton of the phosphinic acid protonates the hydroxyl group, enhancing the leaving group ability. Simultaneously, the oxo group of phosphinic acid operates as a base abstracting the nucleophilic proton and thus enhancing the nucleophilicity. This reaction will open up new atom efficient techniques that enable alcohols to be used as nucleofuges in substitution reactions in the future.
|
|
| 22. |
- Bunrit, Anon, et al.
(författare)
-
H3PO2-Catalyzed Intramolecular Stereospecific Substitution of the Hydroxyl Group in Enantioenriched Secondary Alcohols by N-, O-, and S-Centered Nucleophiles to Generate Heterocycles
- 2020
-
Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 10:2, s. 1344-1352
-
Tidskriftsartikel (refereegranskat)abstract
- The direct intramolecular stereospecific substitution of the hydroxyl group in enantiomerically enriched secondary benzylic, allylic, propargylic, and alkyl alcohols was successfully accomplished by phosphinic acid catalysis. The hydroxyl group was displaced by O-, S-, and N-centered nucleophiles to provide enantioenriched five-membered tetrahydrofuran, pyrrolidine, and tetrahydrothiophene as well as six-membered tetrahydroquinolines and chromanes in up to a 99% yield and 100% enantiospecificity with water as the only byproduct. Mechanistic studies using both experiments and calculations have been performed for substrates generating 5-membered heterocycles. Rate studies show dependences in a catalyst, an internal nucleophile, and an electrophile, however, independence in an external nucleophile, an electrophile, or water. Kinetic isotope effect studies show an inverse KIE of k(H)/k(D) = 0.79. Furthermore, phosphinic acid does not promote S(N)1 reactivity. Computational studies support a bifunctional role of the phosphinic acid in which activation of both nucleofuge and nucleophile occurs in a bridging S(N)2-type transition state. In this transition state, the acidic hydrogen of phosphinic acid protonates the leaving hydroxyl group simultaneously as the oxo group partially deprotonates the nucleophile. Thereby, phosphinic acid promotes the substitution of the nonderivatized hydroxyl group in enantioenriched secondary alcohols by uncharged nucleophiles with conservation of the chirality from the alcohol to the heterocycle.
|
|
| 23. |
- Bunrit, Anon, et al.
(författare)
-
Nucleophilic Substitution of the Hydroxyl Group in Stereogenic Alcohols with Chirality Transfer
- 2016
-
Ingår i: Synlett. - : Georg Thieme Verlag KG. - 0936-5214 .- 1437-2096. ; 27:2, s. 173-176
-
Tidskriftsartikel (refereegranskat)abstract
- A brief overview of the development of direct substitution of the hydroxyl (OH) group of alcohols in our research group is presented. By applying a BrOnsted acid, an intramolecular substitution of the OH group in stereogenic alcohols with chirality transfer was achieved. Noteworthy, the intramolecular substitution has a wide scope in respect to both the nucleophile and also the nucleofuge. A mechanistic study by both experiments and DFT calculations revealed a unique reaction pathway in which the BrOnsted acid operates in a bifunctional manner to promote an S(N)2-type reaction mechanism.
|
|
| 24. |
- Davisayahvorakul, Ratikorn, et al.
(författare)
-
Glycerol Ketal Biobased Product Preparation from Biomass-Derived Reactants Using an H-ZSM-5 Catalyst for Oil Color Painting Application
- 2024
-
Ingår i: ACS Sustainable Chemistry and Engineering. - 2168-0485. ; 12:11, s. 4598-4604
-
Tidskriftsartikel (refereegranskat)abstract
- Condensation of glycerol with bioderived carbonyls yields cyclic ketals with unique properties. In this study, efficient solvent-free heterogeneously catalyzed ketalization has been achieved to give the corresponding products in good to excellent yields. Substrate-to-glycerol ratios of 1:1 have been used; the reactions were performed at 120 °C for 30 min. By using an acid-treated H-ZSM-5 catalyst, high selectivity to a five-membered ring was achieved. Furthermore, the catalyst could be recycled up to 4 times without losing activity. The ketal from glycerol and levulinic acid (GLK) was isolated and applied as a solvent in oil color paint and showed advantageous properties over commercial paint solvents in terms of aging.
|
|
| 25. |
- Dawange, Monali, et al.
(författare)
-
Selective Aerobic Benzylic Alcohol Oxidation of Lignin Model Compounds : Route to Aryl Ketones
- 2015
-
Ingår i: ChemCatChem. - : Wiley. - 1867-3880 .- 1867-3899. ; 7:3, s. 401-404
-
Tidskriftsartikel (refereegranskat)abstract
- A mild and chemoselective oxidation of the -alcohol in -O-4-ethanoaryl and -O-4-glycerolaryl ethers has been developed. The benzylic alcohols were selectively dehydrogenated to the corresponding ketones in 60-93% yield. A one-pot selective route to aryl ethyl ketones was performed. The catalytic system comprises recyclable heterogeneous palladium, mild reaction conditions, green solvents, and oxygen in air as oxidant. Catalytic amounts of a coordinating polyol were found pivotal for an efficient aerobic oxidation.
|
|
