| 1. |
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| 2. |
- Thomas, HS, et al.
(författare)
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- 2019
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swepub:Mat__t
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| 3. |
- Ademuyiwa, Adesoji O., et al.
(författare)
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Determinants of morbidity and mortality following emergency abdominal surgery in children in low-income and middle-income countries
- 2016
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Ingår i: BMJ Global Health. - : BMJ Publishing Group Ltd. - 2059-7908. ; 1:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resource-poor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally.Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression.Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed.Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas.
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| 4. |
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| 5. |
- Abbaszad Rafi, Abdolrahim, et al.
(författare)
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Copper nanoparticles on controlled pore glass (CPG) as highly efficient heterogeneous catalysts for “click reactions”
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- We herein report that supported copper nanoparticles (CuNPs) on commercially available controlled pore glass (CPG), which exhibit high mechanical, thermal and chemical stability as compared to other silica-based materials, serve as a useful heterogeneous catalyst system for 1,3-dipolar cycloadditions (“click” reactions) between terminal alkynes and organic azides under green chemistry conditions. The supported CuNPs-CPG catalyst exhibited a broad substrate scope and gave the corresponding triazole products in high yields. The CuNPs-CPG catalyst exhibit recyclability and could be reuced multiple times without contaminating the products with Cu.
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| 6. |
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| 7. |
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| 8. |
- Afewerki, Samson, et al.
(författare)
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Direct Regiospecific and Highly Enantioselective Intermolecular α-Allylic Alkylation of Aldehydes by a Combination of Transition-Metal and Chiral Amine Catalysts
- 2012
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 18:10, s. 2972-2977
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Tidskriftsartikel (refereegranskat)abstract
- The first direct intermolecular regiospecific and highly enantioselective a-allylic alkylation of linear aldehydes by a combination of achiral bench-stable Pd0 complexes and simple chiral amines as co-catalysts is disclosed. The co-catalytic asymmetric chemoselective and regiospecific a-allylic alkylation reaction is linked in tandem with in situ reduction to give the corresponding 2-alkyl alcohols with high enantiomeric ratios (up to 98:2 e.r.; e.r.=enantiomeric ratio). It is also an expeditious entry to valuable 2-alkyl substituted hemiacetals, 2-alkyl-butane-1,4-diols, and amines. The concise co-catalytic asymmetric total syntheses of biologically active natural products (e.g., Arundic acid) are disclosed.
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| 9. |
- Afewerki, Samson, et al.
(författare)
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Highly Enantioselective Control of Dynamic Cascade Transformations by Dual Catalysis : Asymmetric Synthesis of Polysubstituted Spirocyclic Oxindoles
- 2015
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Ingår i: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 5:2, s. 1266-1272
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Tidskriftsartikel (refereegranskat)abstract
- The highly enantioselective (up to >99.5:0.5 er) synthesis of polysubstituted spirocyclic oxindoles with four new contiguous stereocenters, including the spiro all-carbon quaternary center, is disclosed. It is accomplished by the highly stereoselective control of a dynamic conjugate/intramolecular allylic alkylation relay sequence based on the synergistic cooperation of metal and chiral amine catalysts in which the careful selection of organic Nand, metal complex, and chiral amine is essential. The intermolecular C-C bond-forming step occurred only when both the metal and chiral amine catalysts were present.
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| 10. |
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| 11. |
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| 12. |
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| 13. |
- Cordova, Armando, 1970-, et al.
(författare)
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A sustainable strategy for production and functionalization of nanocelluloses
- 2019
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Ingår i: Pure and Applied Chemistry. - : Walter de Gruyter GmbH. - 0033-4545 .- 1365-3075. ; 91:5, s. 865-874
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Tidskriftsartikel (refereegranskat)abstract
- A sustainable strategy for the neat production and surface functionalization of nanocellulose from wood pulp is disclosed. It is based on the combination of organocatalysis and click chemistry (organoclick chemistry) and starts with nanocellulose production by organic acid catalyzed hydrolysis and esterification of the pulp under neat conditions followed by homogenization. This nanocellulose fabrication route is scalable, reduces energy consumption and the organic acid can be efficiently recycled. Next, the surface is catalytically engineered by organoclick chemistry, which allows for selective and versatile attachment of different organic molecules (e.g. fluorescent probes, catalyst and pharmaceuticals). It also enables binding of metal ions and nanoparticles. This was exemplified by the fabrication of a heterogeneous nanocellulose palladium nanoparticle catalyst, which is used for Suzuki cross-coupling transformations in water. The disclosed surface functionalization methodology is broad in scope and applicable to different nanocelluloses and cellulose based materials as well.
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| 14. |
- Córdova, Armando, et al.
(författare)
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Amino Acid-Catalyzed Neogenesis of Carbohydrates : A Plausible Ancient Transformation
- 2005
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 11:16, s. 4772-4784
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Tidskriftsartikel (refereegranskat)abstract
- Hexose sugars play a fundamental role in vital biochemical processes and their biosynthesis is achieved through enzyme-catalyzed pathways. Herein we disclose the ability of amino acids to catalyze the asymmetric neogenesis of carbohydrates by sequential cross-aldol reactions. The amino acids mediate the asymmetric de novo synthesis of natural L- and D-hexoses and their analogues with excellent stereoselectivity in organic solvents. In some cases, the four new stereocenters are assembled with almost absolute stereocontrol. The unique feature of these results is that, when an amino acid is employed as the catalyst, a single reaction sequence can convert a protected glycol aldehyde into a hexose in one step. For example, proline and its derivatives catalyze the asymmetric neogenesis of allose with >99 % ee in one chemical manipulation. Furthermore, all amino acids tested catalyzed the asymmetric formation of natural sugars under prebiotic conditions, with alanine being the smallest catalyst. The inherent simplicity of this catalytic process suggests that a catalytic prebiotic “gluconeogenesis” may occur, in which amino acids transfer their stereochemical information to sugars. In addition, the amino acid catalyzed stereoselective sequential cross-aldol reactions were performed as a two-step procedure with different aldehydes as acceptors and nucleophiles. The employment of two different amino acids as catalysts for the iterative direct aldol reactions enabled the asymmetric synthesis of deoxysugars with >99 % ee. In addition, the direct amino acid catalyzed C2+C2+C2 methodology is a new entry for the short, highly enantioselective de novo synthesis of carbohydrate derivatives, isotope-labeled sugars, and polyketide natural products. The one-pot asymmetric de novo syntheses of deoxy and polyketide carbohydrates involved a novel dynamic kinetic asymmetric transformation (DYKAT) mediated by an amino acid.
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| 15. |
- Córdova, Armando, et al.
(författare)
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Plausible origins of homochirality in the amino acid catalyzed neogenesis of carbohydrates
- 2005
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 2005, s. 2047-2049
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Tidskriftsartikel (refereegranskat)abstract
- The intrinsic ability of amino acids to catalyze the asymmetric formation of carbohydrates, which enzymes have mediated for millions of years, with significant amplification of enantiomeric excess suggests a plausible ancient catalytic process for the evolution of homochirality.
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| 16. |
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| 17. |
- Deiana, Luca, et al.
(författare)
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Catalytic Asymmetric Aziridination of alpha,beta-Unsaturated Aldehydes
- 2011
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 17:28, s. 7904-7917
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Tidskriftsartikel (refereegranskat)abstract
- The development, scope, and application of the highly enantioselective organocatalytic aziridination of α,β-unsaturated aldehydes is presented. The aminocatalytic azirdination of α,β-unsaturated aldehydes enables the asymmetric formation of β-formyl aziridines with up to >19:1 d.r. and 99 % ee. The aminocatalytic aziridination of α-monosubstituted enals gives access to terminal α-substituted-α-formyl aziridines in high yields and up to 99 % ee. In the case of the organocatalytic aziridination of disubstituted α,β-unsaturated aldehydes, the transformations were highly diastereo- and enantioselective and give nearly enantiomerically pure β-formyl-functionalized aziridine products (99 % ee). A highly enantioselective one-pot cascade sequence based on the combination of asymmetric amine and N-heterocyclic carbene catalysis (AHCC) is also disclosed. This one-pot three-component co-catalytic transformation between α,β-unsaturated aldehydes, hydroxylamine derivatives, and alcohols gives the corresponding N-tert-butoxycarbonyl and N-carbobenzyloxy-protected β-amino acid esters with ee values ranging from 92-99 %. The mechanisms and stereochemistry of all these catalytic transformations are also discussed.
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| 18. |
- Deiana, Luca, 1982-, et al.
(författare)
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Catalytic asymmetric aziridination of α,β-unsaturated aldehydes
- 2011
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 17:28, s. 7904-7917
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Tidskriftsartikel (refereegranskat)abstract
- The development, scope, and application of the highly enantioselective organocatalytic aziridination of α,β-unsaturated aldehydes is presented. The aminocatalytic azirdination of α,β-unsaturated aldehydes enables the asymmetric formation of β-formyl aziridines with up to >19:1 d.r. and 99% ee. The aminocatalytic aziridination of α-monosubstituted enals gives access to terminal α-substituted-α-formyl aziridines in high yields and upto 99% ee. In the case of the organocatalytic aziridination of disubstituted α,β-unsaturated aldehydes, the transformations were highly diastereo- and enantioselective and give nearly enantiomerically pure β-formyl-functionalized aziridine products (99% ee). A highly enantioselective one-pot cascade sequence based on the combination of asymmetric amine and N-heterocycliccarbene catalysis (AHCC) is also disclosed. This one-pot three-component co-catalytic transformation between α,β-unsaturated aldehydes, hydroxylamine derivatives, and alcohols gives the corresponding N-tert-butoxycarbonyl and N-carbobenzyloxy-protected β-amino acid esters with ee values ranging from 92–99%. The mechanisms and stereochemistry of all these catalytic transformations are also discussed.
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| 19. |
- Deiana, Luca, et al.
(författare)
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Catalytic asymmetric aziridination of α, β- unsaturated aldehydes
- 2011
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Ingår i: Abstracts of Papers, 242nd ACS National Meeting & Exposition, Denver, CO, United States, August 28-September 1, 2011. - : American Chemical Society.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The development, scope and application of the highly enantioselective organocatalytic aziridination of a, b- unsaturated aldehydes is presented. The aminocatalytic aziridination of a, b- unsaturated aldehydes enables the asymmetric formation of b-formylaziridines with up to >19:1 dr and 99% ee. The aminocatalytic aziridination of a-monosobstituted enals gives access to terminal a-substituted-a-formyl aziridines in high yields and up to 99% ee. In the case of the organocatalytic aziridination of disubstituted a, b-unsaturated aldehydes, the transformations gives nearly enantiomeric pure b-formyl-functionalized aziridine products. A higly enantioselective one-pot cascade sequence based on combination of asymmetric amine and N-heterocyclic carbene catalysis is also disclosed. This transformation gives the corresponding N-Boc and N-Cbz protected b-amino acid esters with ee´s ranging from 92-99%.
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| 20. |
- Duan, Ran, 1987-, et al.
(författare)
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Acid-Catalyzed Synthesis of Foamed Materials from Renewable Sources
- 2014
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 53:45, s. 17597-17603
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Tidskriftsartikel (refereegranskat)abstract
- In this study, lightweight biobased foamed materials were successfully synthesized by the modification of renewable polysaccharides, such as starch and microcrystalline cellulose. Low-cost and nontoxic organic acids were utilized as catalysts in the first-step esterification reaction of the synthesis. The effects of different reaction conditions on the water absorbency and weight loss of freeze-casted polysaccharide–citrate–chitosan foams are discussed. Physical properties, such as pore-size distributions and compressive stress–strain curves, of the foams were determined. The characterization results show that the amide bonds formed between the carboxylic acid groups of polysaccharide–citrate and the amino groups of chitosan are crucial to the foamed material’s performance.
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| 21. |
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| 22. |
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| 23. |
- Eivazihollagh, Alireza, et al.
(författare)
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One-pot synthesis of cellulose-templated copper nanoparticles with antibacterial properties
- 2017
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Ingår i: Materials letters (General ed.). - : Elsevier BV. - 0167-577X .- 1873-4979. ; 187, s. 170-172
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Tidskriftsartikel (refereegranskat)abstract
- We report a facile in situ synthesis of spherical copper nanoparticles (NPs) templated by a gelled cellulose II matrix under alkaline aqueous reaction conditions. In under 20 min, the hybrid material could be obtained in a one-pot reaction. Field-emission scanning electron microscopy (FE-SEM) revealed that the polycrystalline NPs of 200–500 nm were well distributed in the regenerated cellulose matrix. The average Cu crystallite size was of the order of 20 nm, as estimated from both X-ray diffraction (XRD) and FE-SEM. XRD data also indicated that the composite contained up to approximately 20% Cu2O. In suspensions containing the hybrid material, growth of Escerichia coli and Staphylococcus aureus strains was inhibited by 80% and 95%, respectively, after 72 h. The synthesis procedure offers a general approach to designing various low-cost hybrid materials of almost any shape, and the concept could be extended to utilization areas such as catalysis, functional textiles, and food packaging as well as to electronic applications.
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| 24. |
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| 25. |
- Guangning, Ma, et al.
(författare)
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Accelerating Amine-Catalyzed Asymmetric Reactions by Intermolecular Cooperative Thiourea/Oxime Hydrogen-Bond Catalysis
- 2021
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Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; 2021:21, s. 3043-3049
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Tidskriftsartikel (refereegranskat)abstract
- The ability of intermolecular cooperative thiourea/oxime hydrogen-bond catalysis for improving and accelerating asymmetric aminocatalysis is presented. The two readily available hydrogen-bond-donating catalysts operates in synergy with a chiral amine catalyst to accomplish highly stereoselective transformations. The synergistic catalyst systems simultaneously activate both electrophiles and nucleophiles, and make the transformations more chemo- and stereoselective. This was exemplified by performing co-catalytic enantioselective direct intermolecular α-alkylation reactions of aldehydes, direct aldol reactions, and asymmetric conjugate reactions, which gave the corresponding products in high yields and enantiomeric ratios.
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| 26. |
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| 27. |
- Ibrahem, Ismail, et al.
(författare)
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Catalytic enantioselective 5-hydroxyisoxazolidine synthesis : An asymmetric entry to beta-amino acids
- 2008
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Ingår i: Synthesis (Stuttgart). - : Georg Thieme Verlag KG. - 0039-7881 .- 1437-210X. ; :7, s. 1153-1157
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Tidskriftsartikel (refereegranskat)abstract
- The highly chemo- and enantioselective organocatalytic tandem reaction between N-carbamate-protected hydroxylamines and a,p-unsaturated aldehydes is presented. The reaction represents a unique entry for the asymmetric synthesis of 5-hydroxyisoxazolidines, oxazolidin-5-ones or gamma-hydroxyamino alcohols in high yields and 90-99% ee. A procedure for the conversion of the oxazolidin-5-ones into the corresponding beta-amino acids is also described.
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| 28. |
- Ibrahem, Ismail, et al.
(författare)
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Copper Nanoparticles on Controlled Pore Glass and TEMPO for the Aerobic Oxidation of Alcohols
- 2018
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Ingår i: ChemNanoMat. - : Wiley. - 2199-692X. ; 4:1, s. 71-75
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we report on the facile synthesis of a heterogeneous copper nanocatalyst and its combination with 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) for the aerobic oxidation of alcohols to their corresponding carbonyl compounds. This low cost copper nanocatalyst was found to exhibit excellent recyclability, making it a highly attractive catalytic system from an economical and environmental point of view. Extensive characterization of the catalyst by a number of techniques revealed that it was comprised of well-dispersed Cu(I/II) nanoparticles with an average size of around 6nm.
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| 29. |
- Ibrahem, Ismail, 1972-
(författare)
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Development of organocatalytic asymmetric transformations
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The ability of amino acids and amino acid derivatives to mediate various organocatalytic asymmetric transformations has been investigated and applied in the development of various reactions. This work describes the development of a direct catalytic asymmetric α-aminomethylation of ketones and aldehydes, a catalytic asymmetric aziridination, hydrophosphination and amination of α,β-unsaturated aldehydes.
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| 30. |
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| 31. |
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| 32. |
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| 33. |
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| 34. |
- Ibrahem, Ismail, et al.
(författare)
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Enantioselective addition of aldehydes to amines via combined catalytic biomimetic oxidation and organocatalytic C-C bond formation.
- 2005
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Ingår i: Tetrahedron Letters. - : Elsevier BV. - 0040-4039 .- 1359-8562. ; 46:23, s. 3965-3968
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Tidskriftsartikel (refereegranskat)abstract
- The biomimetic catalytic enantioselective addn. of aldehydes to amines is reported. This was accomplished by combining biomimetic coupled catalytic aerobic oxidn. of amines involving ruthenium-induced dehydrogenation and organocatalytic asym. Mannich reactions. The one-pot reactions furnished β-amino aldehyde and α-amino acid derivs. in high yields with excellent chemoselectivity and enantioselectivity. [on SciFinder(R)]
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| 35. |
- Ibrahem, Ismail, et al.
(författare)
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Enantioselective Conjugate Silyl Additions to alpha,beta-Unsaturated Aldehydes Catalyzed by Combination of Transition Metal and Chiral Amine Catalysts
- 2011
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Ingår i: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 353:2-3, s. 245-252
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Tidskriftsartikel (refereegranskat)abstract
- We report that transition metal-catalyzed nucleophilic activation can be combined with chiral amine-catalyzed iminium activation as exemplified by the unprecedented enantioselective conjugate addition of a dimethylsilanyl group to alpha,beta-unsaturated aldehydes. These reactions proceed with excellent 1,4-selectivity to afford the corresponding beta-silyl aldehyde products 3 in high yields and up to 97:3 er using inexpensive bench stable copper salts and simple chiral amine catalysts. The reaction can also generate a quaternary stereocenter with good enantioselectivity. Density functional calculations are performed to elucidate the reaction mechanism and the origin of enantioselectivity.
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| 36. |
- Ibrahem, Ismail, et al.
(författare)
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Enantioselective conjugate silyl additions to α,β-unsaturated aldehydes catalyzed by combination of transition metal and chiral amine catalysts
- 2011
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Ingår i: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 353:2+3, s. 245-252
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Tidskriftsartikel (refereegranskat)abstract
- We report that transition metal-catalyzed nucleophilic activation can be combined with chiral amine-catalyzed iminium activation as exemplified by the unprecedented enantioselective conjugate addition of a dimethylsilanyl group to α,β-unsaturated aldehydes. These reactions proceed with excellent 1,4-selectivity to afford the corresponding β-silyl aldehyde products 3 in high yields and up to 97:3 er using inexpensive bench stable copper salts and simple chiral amine catalysts. The reaction canalso generate a quaternary stereocenter with goodenantioselectivity. Density functional calculations are performed to elucidate the reaction mechanism and the origin of enantioselectivity.
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| 37. |
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| 38. |
- Ibrahem, Ismail, et al.
(författare)
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Enantioselective Organocatalytic Hydrophosphination of α,β-Unsaturated Aldehydes
- 2007
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 46:24, s. 4507-4510
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Tidskriftsartikel (refereegranskat)abstract
- Keeping it simple: Optically active phosphine derivatives can be obtained in high yields and in up to 99% ee by using simple chiral amines to catalyze the hydrophosphination of α,β-unsaturated aldehydes (see scheme, green sphere = chiral group). The synthetic utility of this highly chemo- and enantioselective transformation was exemplified by the one-pot asymmetric synthesis of β-phosphine oxide acids.
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| 39. |
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| 40. |
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| 41. |
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| 42. |
- Ibrahem, Ismail, et al.
(författare)
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One-pot three-component catalytic asymmetric synthesis of homoallylboronates
- 2012
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Ingår i: ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY. Vol 243. - : American Chemical Society (ACS). ; , s. 889-INOR-
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Konferensbidrag (refereegranskat)abstract
- 1. A novel one-pot three-component catalytic enantioselective reaction between bis(pinacolato)diboron, enals and 2-(triphenylphosphoranylidene)acetate esters employing inexpensive bench stable Cu salts and simple chiral amine as co-catalysts is presented. The reaction proceeds via a tandem catalytic asymmetric conjugate borane addition/Wittig sequence where the b-boration step is 1,4-selective and gives the corresponding homoallylboronate products with high enantiomeric ratios (up to 97.5:2.5 er).2. The direct intermolecular regiospecific and highly enantioselective a-allylic alkylation of linear aldehydes by combination of achiral bench stable Pd(0) complexes and simple chiral amines as co-catalysts is disclosed. The co-catalytic asymmetric chemoselective and regiospecific a-allylic alkylation reaction is linked in tandem with in situ reduction to give the corresponding 2-alkyl alcohols with high enantiomeric ratios (up to 98:2 er). It is also an expeditious entry to valuable 2-alkyl substituted hemiacetals and 2-alkyl-butane-1,4-diols.
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| 43. |
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| 44. |
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| 45. |
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| 46. |
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| 47. |
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| 48. |
- Ibrahem, Ismail, et al.
(författare)
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Organocatalytic asymmetric hydrophosphination of alpha,beta-unsaturated aldehydes : Development, mechanism and DFT calculations
- 2008
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Ingår i: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 350:11-12, s. 1875-1884
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Forskningsöversikt (refereegranskat)abstract
- The development and mechanism of the highly chemo- and enantioselective organocatalytic hydrophosphination reaction of alpha,beta-unsaturated aldehydes is presented. The reactions are catalyzed by protected chiral diarylprolinol derivatives and give access to optically active phosphine derivatives in high yields with up to 99% ee. The organocatalytic addition of other phosphorus nucleophiles was also investigated. The origin of the high enantioselectivity for the reaction with diphenylphosphine as the nucleophile is investigated by density functional theory calculations.
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| 49. |
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| 50. |
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