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Affiliation(s)
- Vincent Vermaak
- Catalysis & Synthesis Research Group Research Focus Area: Chemical Resource Beneficiation North-West University 11 Hofmann Street Potchefstroom 2520 South Africa
| | - Hermanus C. M. Vosloo
- Catalysis & Synthesis Research Group Research Focus Area: Chemical Resource Beneficiation North-West University 11 Hofmann Street Potchefstroom 2520 South Africa
| | - Andrew J. Swarts
- Catalysis & Synthesis Research Group Research Focus Area: Chemical Resource Beneficiation North-West University 11 Hofmann Street Potchefstroom 2520 South Africa
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Tole TT, Jordaan JHL, Vosloo HCM. α-Pyridinyl Alcohols, α,α'-Pyridine Diols, α-Bipyridinyl Alcohols, and α,α'-Bipyridine Diols as Structure Motifs Towards Important Organic Molecules and Transition Metal Complexes. Curr Org Synth 2020; 17:344-366. [PMID: 32091340 DOI: 10.2174/1570179417666200212111049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 11/15/2019] [Accepted: 12/28/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND The preparation and use of pyridinyl alcohols as ligands showed incredible increment in the past three decades. Important property of pyridinyl alcoholato ligands is their strong basicity, which is mainly due to the lack of resonance stabilization of the corresponding anion. This strongly basic anionic nature gives them high ability to make bridges between metal centers rather than to bind to only one metal center in a terminal fashion. They are needed as ligands due to their ability to interact with transition metals both covalently (with oxygen) and hemilabile coordination (through nitrogen). OBJECTIVE The review focuses on the wide application of α-pyridinyl alcohols, α,α'-pyridine diols, α- bipyridinyl alcohols, and α,α'-bipyridine diols as structure motifs in the preparation of important organic molecules which is due to their strongly basic anionic nature. CONCLUSION It is clear from the review that in addition to their synthetic utility in the homogeneous and asymmetric catalytic reactions, the preparation of the crown ethers, cyclic and acyclic ethers, coordinated borates (boronic esters), pyridinyl-phosphine ligands, pyridinyl-phosphite ligands, and pyridinyl-phosphinite ligands is the other broad area of application of pyridinyl alcohols. In addition to the aforementioned applications they are used for modeling mode of action of enzymes and some therapeutic agents. Their strongly basic anionic nature gives them high ability to make bridges between metal centers rather than to bind to only one metal center in a terminal fashion in the synthesis of transition metal cluster complexes. Not least numbers of single molecule magnets that can be used as storage of high density information were the result of transition metal complexes of pyridinyl alcoholato ligands.
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Affiliation(s)
- Tegene T Tole
- Research Focus Area for Chemical Resource Beneficiation, Catalysis and Synthesis Research Group, North-West University, Hoffmann Street, 2531 Potchefstroom, South Africa
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Tole TT, Jordaan JHL, Vosloo HCM. Catalysis of linear alkene metathesis by Grubbs-type ruthenium alkylidene complexes containing hemilabile α,α-diphenyl-(monosubstituted-pyridin-2-yl)methanolato ligands. Beilstein J Org Chem 2019; 15:194-209. [PMID: 30745994 PMCID: PMC6350883 DOI: 10.3762/bjoc.15.19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Accepted: 12/21/2018] [Indexed: 12/03/2022] Open
Abstract
Four new Grubbs-type precatalysts [RuCl(H2IMes)(O^N)(=CHPh)], where [O^N = α,α-diphenyl-(3-methylpyridin-2-yl)methanolato, α,α-diphenyl-(4-methylpyridin-2-yl)methanolato, α,α-diphenyl-(5-methylpyridin-2-yl)methanolato and α,α-diphenyl-(3-methoxypyridin-2-yl)methanolato] were synthesized and tested for their activity, stability and selectivity in the 1-octene metathesis reaction. Overall the precatalysts showed good activity and high stability for the metathesis of 1-octene at temperatures above 80 °C and up to 110 °C. Selectivities towards the primary metathesis products, i.e., 7-tetradecene and ethene, above 85% were obtained with all the precatalysts at 80 and 90 °C. High selectivities were also observed at 100 °C for the 4-Me- and 3-OMe-substituted precatalysts. With an increase in temperature an increase in isomerisation products and secondary metathesis products were observed with the latter reaching values >20% for the 3-OMe- and 3-Me-substituted precatalysts at 110 and 100 °C, respectively. All the precatalysts exhibits first-order kinetics at 80 °C with the 3-substituted precatalysts the slowest. The behaviour of the 3-substituted precatalysts can be attributed to electronic and steric effects associated with the adjacent bulky phenyl groups.
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Affiliation(s)
- Tegene T Tole
- Research Focus Area for Chemical Resource Beneficiation, Catalysis and Synthesis Research Group, North-West University, Hoffmann Street, 2531 Potchefstroom, South Africa.,Department of Chemistry, College of Natural and Computational Sciences, Hawassa University, Hawassa, Ethiopia
| | - Johan H L Jordaan
- Research Focus Area for Chemical Resource Beneficiation, Catalysis and Synthesis Research Group, North-West University, Hoffmann Street, 2531 Potchefstroom, South Africa
| | - Hermanus C M Vosloo
- Research Focus Area for Chemical Resource Beneficiation, Catalysis and Synthesis Research Group, North-West University, Hoffmann Street, 2531 Potchefstroom, South Africa
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Breckwoldt NCC, Goosen NJ, Vosloo HCM, Van der Gryp P. Kinetic evaluation of the hydroformylation of the post-metathesis product 7-tetradecene using a bulky phosphite-modified rhodium catalyst. REACT CHEM ENG 2019. [DOI: 10.1039/c8re00239h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A mechanism-based rate model was applied for the hydroformylation of the post-metathesis product 7-tetradecene using a bulky phosphite-modified rhodium catalyst.
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Affiliation(s)
| | - Neill J. Goosen
- Department of Process Engineering
- University of Stellenbosch
- Matieland 7602
- South Africa
| | - Hermanus C. M. Vosloo
- Research Focus Area for Chemical Resource Beneficiation
- Catalysis and Synthesis Research Group
- North-West University
- Potchefstroom
- South Africa
| | - Percy Van der Gryp
- School of Chemical and Minerals Engineering
- Research Focus Area for Chemical Resource Beneficiation
- North-West University
- Potchefstroom 2522
- South Africa
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Mohammed AD, Young DA, Vosloo HCM. Synthesis of high-performance superabsorbent glycerol acrylate-cross-linked poly (acrylic acid). Res Chem Intermed 2016. [DOI: 10.1007/s11164-016-2754-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Marx FTI, Jordaan JHL, Lachmann G, Vosloo HCM. A comparison of low and high activity precatalysts: do the calculated energy barriers during the self-metathesis reaction of 1-octene correlate with the precatalyst metathesis activity? J Comput Chem 2014; 35:1464-71. [PMID: 24866263 DOI: 10.1002/jcc.23642] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 05/05/2014] [Accepted: 05/06/2014] [Indexed: 01/02/2023]
Abstract
The self-metathesis reaction of 1-octene with several well-known Grubbs-type precatalysts and the new Z-selective Grubbs precatalyst were studied with molecular modeling. The obtained Gibbs-free energy values for all the steps during the productive metathesis of 1-octene were compared to the values obtained for some low catalytic activity precatalysts. Determining how the Gibbs-free energy values of highly active precatalysts compare to that of low catalytic activity precatalysts gave a deeper insight into the mechanism. The questionable correlation of the theoretically observed trends with those obtained experimentally does point to the need to be very cautious when making assumptions from theoretical results without a sufficiently large dataset.
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Affiliation(s)
- Frans T I Marx
- Research Focus Area for Chemical Resource Beneficiation:, Catalysis and Synthesis Group, North-West University, Hoffmann Street, Potchefstroom, 2520, South Africa
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Marx FTI, Jordaan JHL, Lachmann G, Vosloo HCM. A molecular modeling study of the changes of some steric properties of the precatalysts during the olefin metathesis reaction. J Comput Chem 2014; 35:1457-63. [PMID: 24866082 DOI: 10.1002/jcc.23641] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 05/05/2014] [Accepted: 05/07/2014] [Indexed: 12/29/2022]
Abstract
The productive self-metathesis of 1-octene with a series of new phosphine ligated Grubbs-type precatalysts was studied. The resulting structures were used to compare some steric properties of the new precatalysts with those of well-known precatalysts. The possibility of α-CC agnostic stabilization as well as the ability of the ligands to shield the metal was studied. A comparison of the obtained data, pointed to the unlikelihood that α-CC agostic stabilization is a major contribution to the stabilization of the various metallacyclobutane rings. The similarity in the ability of the ligands to shield the metal also raised questions about the comparison of experimentally observed trends with those obtained theoretically.
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Affiliation(s)
- Frans T I Marx
- Research Focus Area for Chemical Resource Beneficiation: Catalysis and Synthesis Group, North-West University, Hoffmann Street, Potchefstroom, 2520, South Africa
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du Toit JI, Jordaan M, Huijsmans CAA, Jordaan JHL, van Sittert CGCE, Vosloo HCM. Improved metathesis lifetime: chelating pyridinyl-alcoholato ligands in the second generation Grubbs precatalyst. Molecules 2014; 19:5522-37. [PMID: 24786690 PMCID: PMC6272008 DOI: 10.3390/molecules19055522] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Revised: 04/22/2014] [Accepted: 04/24/2014] [Indexed: 11/16/2022] Open
Abstract
Hemilabile ligands can release a free coordination site "on demand" of an incoming nucleophilic substrate while occupying it otherwise. This is believed to increase the thermal stability and activity of catalytic systems and therefore prevent decomposition via free coordination sites. In this investigation chelating pyridinyl-alcoholato ligands were identified as possible hemilabile ligands for incorporation into the second generation Grubbs precatalyst. The O,N-alcoholato ligands with different steric bulk could be successfully incorporated into the precatalysts. The incorporation of the sterically hindered, hemilabile O,N-ligands improved the thermal stability, activity, selectivity and lifetime of these complexes towards the metathesis of 1-octene. A decrease in the activity of the second generation Grubbs precatalyst was additionally observed after incorporating a hemilabile O,N-ligand with two phenyl groups into the system, while increasing their lifetime.
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Affiliation(s)
- Jean I du Toit
- Research Focus Area for Chemical Resource Beneficiation, Catalysis and Synthesis Research Group, North-West University, Potchefstroom 2520, South Africa.
| | - Margaritha Jordaan
- Research Focus Area for Chemical Resource Beneficiation, Catalysis and Synthesis Research Group, North-West University, Potchefstroom 2520, South Africa.
| | - Carlijn A A Huijsmans
- Research Focus Area for Chemical Resource Beneficiation, Catalysis and Synthesis Research Group, North-West University, Potchefstroom 2520, South Africa.
| | - Johannes H L Jordaan
- Research Focus Area for Chemical Resource Beneficiation, Catalysis and Synthesis Research Group, North-West University, Potchefstroom 2520, South Africa.
| | - Cornelia G C E van Sittert
- Research Focus Area for Chemical Resource Beneficiation, Catalysis and Synthesis Research Group, North-West University, Potchefstroom 2520, South Africa.
| | - Hermanus C M Vosloo
- Research Focus Area for Chemical Resource Beneficiation, Catalysis and Synthesis Research Group, North-West University, Potchefstroom 2520, South Africa.
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Mohammed AD, Young DA, Vosloo HCM. Synthesis and study of superabsorbent properties of acryloylated starch ester grafted with acrylic acid. STARCH-STARKE 2014. [DOI: 10.1002/star.201300174] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Aliyu D. Mohammed
- Research Focus Area for Chemical Resource Beneficiation, Catalysis and Synthesis Research Group; North-West University; Potchefstroom South Africa
| | - Desmond A. Young
- Research Focus Area for Chemical Resource Beneficiation, Catalysis and Synthesis Research Group; North-West University; Potchefstroom South Africa
| | - Hermanus C. M. Vosloo
- Research Focus Area for Chemical Resource Beneficiation, Catalysis and Synthesis Research Group; North-West University; Potchefstroom South Africa
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Marx FTI, Jordaan JHL, Vosloo HCM. DFT investigation of the 1-octene metathesis reaction mechanism with the Phobcat precatalyst. J Mol Model 2009; 15:1371-81. [DOI: 10.1007/s00894-009-0513-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2008] [Accepted: 03/06/2009] [Indexed: 10/20/2022]
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Otto DP, Vosloo HCM, Liebenberg W, de Villiers MM. Development of microporous drug-releasing films cast from artificial nanosized latexes of poly(styrene-co-methyl methacrylate) or poly(styrene-co-ethyl methacrylate). Eur J Pharm Biopharm 2008; 69:1121-34. [PMID: 18417330 DOI: 10.1016/j.ejpb.2008.02.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2007] [Revised: 01/25/2008] [Accepted: 02/01/2008] [Indexed: 11/18/2022]
Abstract
Two sets of copolymers comprising of styrene and either methyl or ethyl methacrylate as comonomer were conveniently synthesized by microemulsion copolymerization. The purified materials were characterized by GPC-MALLS and were shown to form artificial nanolatexes in THF. ATR-FTIR analysis revealed differences in copolymer composition and based on the copolymer properties, a selection of copolymers was chosen to cast drug-loaded, microporous films that exhibit microencapsulation of drug agglomerates. The contact angles of the copolymers suggested potential applications in medical devices to prevent the formation of bacterial biofilms that commonly result in infections. Additionally, the different copolymeric films showed two phases of drug release characterized by a rapid initial drug release followed by a zero-order phase. Depending on the application, one could select the copolymer films that best suited the application i.e. for short-term drug release applications such as urinary catheters or long-term applications such as artificial implants.
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Affiliation(s)
- Daniel P Otto
- School of Pharmacy, University of Wisconsin - Madison, WI 53705, USA.
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Otto DP, Vosloo HCM, de Villiers MM. Application of Size Exclusion Chromatography in the Development and Characterization of Nanoparticulate Drug Delivery Systems. J LIQ CHROMATOGR R T 2007. [DOI: 10.1080/10826070701540076] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Daniel P. Otto
- a Research Institute for Industrial Pharmacy, North‐West University , Potchefstroom, South Africa
| | | | - Melgardt M. de Villiers
- c Pharmaceutical Sciences Division , School of Pharmacy, University of Wisconsin‐Madison , Madison, Wisconsin, USA
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Otto DP, Vosloo HCM, Liebenberg W, de Villiers MM. Effects of the cosurfactant 1-butanol and feed composition on nanoparticle properties produced by microemulsion copolymerization of styrene and methyl methacrylate. J Appl Polym Sci 2007. [DOI: 10.1002/app.27536] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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