The Experts below are selected from a list of 87 Experts worldwide ranked by ideXlab platform
Howard M. Colquhoun - One of the best experts on this subject based on the ideXlab platform.
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Exchange Reactions of Poly(arylene ether ketone) Dithioketals with Aliphatic Diols: Formation and Deprotection of Poly(arylene ether ketal)s
Macromolecules, 2017Co-Authors: Ioannis Manolakis, Paul Cross, Howard M. ColquhounAbstract:The Dithioketal derivatives of industrially important, semicrystalline poly(arylene ether ketone)s undergo facile exchange with aliphatic diols in the presence of N-bromo-succinimide to give a range of novel poly(arylene ether ketal)s. These are amorphous and readily soluble in a wide range of organic solvents. Although generally stable under ambient conditions, they undergo rapid and quantitative hydrolysis in the presence of acids to regenerate the original polyketones. The poly(ether ketal)s reported here are not accessible from ketal-type monomers, nor can they be obtained by direct reaction of poly(ether ketone)s with aliphatic diols. The starting polyketones are essentially unchanged after sequential Dithioketalization, Dithioketal–ketal exchange, ketal hydrolysis, and reDithioketalization. Poly(arylene ether ketal)s provide a new approach to the processing of poly(arylene ether ketone)s into carbon fiber composite materials.
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Exchange Reactions of Poly(arylene ether ketone) Dithioketals with Aliphatic Diols: Formation and Deprotection of Poly(arylene ether ketal)s
2017Co-Authors: Ioannis Manolakis, Paul Cross, Howard M. ColquhounAbstract:The Dithioketal derivatives of industrially important, semicrystalline poly(arylene ether ketone)s undergo facile exchange with aliphatic diols in the presence of N-bromo-succinimide to give a range of novel poly(arylene ether ketal)s. These are amorphous and readily soluble in a wide range of organic solvents. Although generally stable under ambient conditions, they undergo rapid and quantitative hydrolysis in the presence of acids to regenerate the original polyketones. The poly(ether ketal)s reported here are not accessible from ketal-type monomers, nor can they be obtained by direct reaction of poly(ether ketone)s with aliphatic diols. The starting polyketones are essentially unchanged after sequential Dithioketalization, Dithioketal–ketal exchange, ketal hydrolysis, and reDithioketalization. Poly(arylene ether ketal)s provide a new approach to the processing of poly(arylene ether ketone)s into carbon fiber composite materials
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Reversible, Nondegradative Conversion of Crystalline Aromatic Poly(ether ketone)s into Organo-Soluble Poly(ether Dithioketal)s
Macromolecules, 2009Co-Authors: Howard M. Colquhoun, Philip Hodge, François P. V. Paoloni, P. Terry Mcgrail, Paul CrossAbstract:Crystalline aromatic poly(ether ketone)s such as PEEK and PEK may be cleanly and reversibly derivatized by Dithioketalization of the carbonyl groups with 1,2-ethanedithiol or 1,3-propanedithiol under strong acid conditions. The resulting 1,3-dithiolane and 1,3-dithiane polymers are hydrolytically stable, amorphous, and readily soluble in organic solvents such as chloroform and THF and are thus (unlike their parent polymers) easily characterized by gel permeation chromatography (GPC). GPC analysis of a range of derivatized PEEK samples using light-scattering detection revealed, in some instances, a bimodal molecular weight distribution with a small but potentially significant (and previously undetected) very high-molecular-weight fraction.
Paul Cross - One of the best experts on this subject based on the ideXlab platform.
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Exchange Reactions of Poly(arylene ether ketone) Dithioketals with Aliphatic Diols: Formation and Deprotection of Poly(arylene ether ketal)s
Macromolecules, 2017Co-Authors: Ioannis Manolakis, Paul Cross, Howard M. ColquhounAbstract:The Dithioketal derivatives of industrially important, semicrystalline poly(arylene ether ketone)s undergo facile exchange with aliphatic diols in the presence of N-bromo-succinimide to give a range of novel poly(arylene ether ketal)s. These are amorphous and readily soluble in a wide range of organic solvents. Although generally stable under ambient conditions, they undergo rapid and quantitative hydrolysis in the presence of acids to regenerate the original polyketones. The poly(ether ketal)s reported here are not accessible from ketal-type monomers, nor can they be obtained by direct reaction of poly(ether ketone)s with aliphatic diols. The starting polyketones are essentially unchanged after sequential Dithioketalization, Dithioketal–ketal exchange, ketal hydrolysis, and reDithioketalization. Poly(arylene ether ketal)s provide a new approach to the processing of poly(arylene ether ketone)s into carbon fiber composite materials.
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Exchange Reactions of Poly(arylene ether ketone) Dithioketals with Aliphatic Diols: Formation and Deprotection of Poly(arylene ether ketal)s
2017Co-Authors: Ioannis Manolakis, Paul Cross, Howard M. ColquhounAbstract:The Dithioketal derivatives of industrially important, semicrystalline poly(arylene ether ketone)s undergo facile exchange with aliphatic diols in the presence of N-bromo-succinimide to give a range of novel poly(arylene ether ketal)s. These are amorphous and readily soluble in a wide range of organic solvents. Although generally stable under ambient conditions, they undergo rapid and quantitative hydrolysis in the presence of acids to regenerate the original polyketones. The poly(ether ketal)s reported here are not accessible from ketal-type monomers, nor can they be obtained by direct reaction of poly(ether ketone)s with aliphatic diols. The starting polyketones are essentially unchanged after sequential Dithioketalization, Dithioketal–ketal exchange, ketal hydrolysis, and reDithioketalization. Poly(arylene ether ketal)s provide a new approach to the processing of poly(arylene ether ketone)s into carbon fiber composite materials
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Reversible, Nondegradative Conversion of Crystalline Aromatic Poly(ether ketone)s into Organo-Soluble Poly(ether Dithioketal)s
Macromolecules, 2009Co-Authors: Howard M. Colquhoun, Philip Hodge, François P. V. Paoloni, P. Terry Mcgrail, Paul CrossAbstract:Crystalline aromatic poly(ether ketone)s such as PEEK and PEK may be cleanly and reversibly derivatized by Dithioketalization of the carbonyl groups with 1,2-ethanedithiol or 1,3-propanedithiol under strong acid conditions. The resulting 1,3-dithiolane and 1,3-dithiane polymers are hydrolytically stable, amorphous, and readily soluble in organic solvents such as chloroform and THF and are thus (unlike their parent polymers) easily characterized by gel permeation chromatography (GPC). GPC analysis of a range of derivatized PEEK samples using light-scattering detection revealed, in some instances, a bimodal molecular weight distribution with a small but potentially significant (and previously undetected) very high-molecular-weight fraction.
Ioannis Manolakis - One of the best experts on this subject based on the ideXlab platform.
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Exchange Reactions of Poly(arylene ether ketone) Dithioketals with Aliphatic Diols: Formation and Deprotection of Poly(arylene ether ketal)s
Macromolecules, 2017Co-Authors: Ioannis Manolakis, Paul Cross, Howard M. ColquhounAbstract:The Dithioketal derivatives of industrially important, semicrystalline poly(arylene ether ketone)s undergo facile exchange with aliphatic diols in the presence of N-bromo-succinimide to give a range of novel poly(arylene ether ketal)s. These are amorphous and readily soluble in a wide range of organic solvents. Although generally stable under ambient conditions, they undergo rapid and quantitative hydrolysis in the presence of acids to regenerate the original polyketones. The poly(ether ketal)s reported here are not accessible from ketal-type monomers, nor can they be obtained by direct reaction of poly(ether ketone)s with aliphatic diols. The starting polyketones are essentially unchanged after sequential Dithioketalization, Dithioketal–ketal exchange, ketal hydrolysis, and reDithioketalization. Poly(arylene ether ketal)s provide a new approach to the processing of poly(arylene ether ketone)s into carbon fiber composite materials.
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Exchange Reactions of Poly(arylene ether ketone) Dithioketals with Aliphatic Diols: Formation and Deprotection of Poly(arylene ether ketal)s
2017Co-Authors: Ioannis Manolakis, Paul Cross, Howard M. ColquhounAbstract:The Dithioketal derivatives of industrially important, semicrystalline poly(arylene ether ketone)s undergo facile exchange with aliphatic diols in the presence of N-bromo-succinimide to give a range of novel poly(arylene ether ketal)s. These are amorphous and readily soluble in a wide range of organic solvents. Although generally stable under ambient conditions, they undergo rapid and quantitative hydrolysis in the presence of acids to regenerate the original polyketones. The poly(ether ketal)s reported here are not accessible from ketal-type monomers, nor can they be obtained by direct reaction of poly(ether ketone)s with aliphatic diols. The starting polyketones are essentially unchanged after sequential Dithioketalization, Dithioketal–ketal exchange, ketal hydrolysis, and reDithioketalization. Poly(arylene ether ketal)s provide a new approach to the processing of poly(arylene ether ketone)s into carbon fiber composite materials
Tokala Ramachandar - One of the best experts on this subject based on the ideXlab platform.
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Α-Amino 1,3-Dithioketal mediated asymmetric synthesis of piperidines (L-733,060) and tetrahydrofuran glycines
Tetrahedron letters, 2008Co-Authors: Franklin A. Davis, Tokala RamachandarAbstract:Sulfinimine-derived α-amino 1,3-dithianes and α-amino carbonyl chiral building blocks, are utilized in asymmetric syntheses of (+)-(tetrahydrofuran-2-yl)glycine and the 2,3-disubstituted piperidine (+)-L-733,060.
Franklin A. Davis - One of the best experts on this subject based on the ideXlab platform.
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α-Amino cyclic Dithioketal mediated asymmetric synthesis of (S)-(-)-α-(N-p-toluenesulfonyl)aminopropiophenone (N-tosyl cathinone)
Arkivoc, 2008Co-Authors: Franklin A. Davis, Jing ChaiAbstract:The asymmetric synthesis of N-tosyl cathinone, a high reactive α-amino ketone, via the addition of 2-lithio-2-phenyl-1,3-dithiane to a sulfinimine (N-sulfinyl imine), is described. It was found that the resistance of N-tosyl α-amino ketones to epimerization is related to the ability of this protecting group to stabilize anions at nitrogen.
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Α-Amino 1,3-Dithioketal mediated asymmetric synthesis of piperidines (L-733,060) and tetrahydrofuran glycines
Tetrahedron letters, 2008Co-Authors: Franklin A. Davis, Tokala RamachandarAbstract:Sulfinimine-derived α-amino 1,3-dithianes and α-amino carbonyl chiral building blocks, are utilized in asymmetric syntheses of (+)-(tetrahydrofuran-2-yl)glycine and the 2,3-disubstituted piperidine (+)-L-733,060.