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Mateo Alajarin - One of the best experts on this subject based on the ideXlab platform.
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recent highlights in Ketenimine chemistry
ChemInform, 2013Co-Authors: Mateo Alajarin, Marta Marinluna, Angel VidalAbstract:Selected recent developments in the chemistry of Ketenimines are presented, demonstrating that heterocumulenes of this class are versatile reactive intermediates in the synthesis of nitrogenated heterocycles. This microreview includes examples of intramolecular nucleophilic and radical additions, biradical cyclizations, 4π- and 6π-electrocyclic ring closures, [2+2], [3+2] and [4+2] cycloadditions, Ketenimine-to-nitrile rearrangements and 1,3-X, 1,5-X and 1,5-H shifts.
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tandem 1 5 hydride shift 6π electrocyclization of Ketenimines and carbodiimides substituted with cyclic acetal and dithioacetal functions experiments and computations
European Journal of Organic Chemistry, 2011Co-Authors: Mateo Alajarin, Mariamar Ortin, Baltasar Bonillo, Pilar Sanchezandrada, Angel VidalAbstract:N-Aryl Ketenimines bearing five- and six-membered cyclic acetal functions - such as 1,3-dioxolane, 1,3-dithiolane, 1,3-dioxane, and 1,3-dithiane systems - at the ortho position of the N-aryl substituent transform on mild thermal treatment into quinolines, through a tandem sequence consisting of a [1,5]-H shift followed by a 6π electrocyclic ring closure. Structurally analogous N-aryl carbodiimides are converted into quinazolines in comparable tandem processes. Similar sequences can be successfully applied to N-thienyl and N-pyrazolyl Ketenimines. DFT calculations have established a two-step mechanism for those conversions, consisting of an initial 1,5-hydride shift and subsequent 6π electrocyclization, and confirm the beneficial effect of the acetal function, which gives hydride character to the migrating hydrogen atom. The capability to promote the H shift depends on the type of acetal function (acetal better than dithioacetal), its ring size (five-membered better than six-membered) and the heterocumulenic fragment (Ketenimine better than carbodiimide). Changing the benzene ring connecting the acetal and Ketenimine functions for a heterocyclic ring has pronounced consequences for the magnitude of the energy barriers.
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domino reactions initiated by intramolecular hydride transfers from tri di arylmethane fragments to Ketenimine and carbodiimide functions
Organic and Biomolecular Chemistry, 2010Co-Authors: Mateo Alajarin, Angel Vidal, Mariamar Ortin, Baltasar Bonillo, Pilar Sanchezandrada, Raulangel OrenesAbstract:The ability of triarylmethane and diarylmethane fragments to behave as hydride donors participating in thermal [1,5]-H shift/6π-ERC tandem processes involving Ketenimine and carbodiimide functions is disclosed. C-Alkyl-C-phenyl Ketenimines N-substituted by a triarylmethane substructure convert into a variety of 3,3,4,4-tetrasubstituted-3,4-dihydroquinolines, as structurally related carbodiimides transform into 3,4,4-trisubstituted-3,4-dihydroquinazolines via transient ortho-azaxylylenes. The first step of these one-pot conversions, the [1,5]-H shift, is considered to be a hydride migration on the basis of the known hydricity of the tri(di)arylmethane fragment and the electrophilicity of the central heterocumulenic carbon atom, whereas the final electrocyclization involves the formation of a sterically congested C–C or C–N bond. In the cases of C,C-diphenyl substituted triarylmethane-Ketenimines the usual 6π-ERC becomes prohibited by the presence of two phenyl rings at each end of the azatrienic system. This situation opens new reaction channels: (a) following the initial hydride shift, the tandem sequence continues with an alternative electrocyclization mode to give 9,10-dihydroacridines, (b) the full sequence is initiated by a rare 1,5 migration of an electron-rich aryl group, followed by a 6π-ERC which leads to 2-aryl-3,4-dihydroquinolines, or (c) a different [1,5]-H shift/6π-ERC sequence involving the initial migration of a hydrogen atom from a methyl group at the ortho position to the nitrogen atom of the Ketenimine function. Diarylmethane-Ketenimines bearing a methyl group at the benzylic carbon atom experience a tandem double [1,5]-H shift, the first one being the usual benzylic hydride transfer whereas the second one involves the methyl group at the initial benzylic carbon atom, the reaction products being 2-aminostyrenes. Diarylmethane-Ketenimines lacking such a methyl group convert into 3,4-dihydroquinolines by the habitual tandem [1,5]-H shift/6π-ERC processes.
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tandem 1 5 hydride shift 1 5 s n cyclization with ethylene extrusion of 1 3 oxathiolane substituted Ketenimines and carbodiimines an experimental and computational study
ChemInform, 2010Co-Authors: Mateo Alajarin, Baltasar Bonillo, Pilar Sanchezandrada, Angel VidalAbstract:Upon heating Ketenimines of type (III) and carbodiimines derived from isocyanates (VIII) undergo unexpected transformation into benzisothiazolones via 1,5-hydride shift, 1,5-electrocyclization, and [3 + 2] cycloreversion.
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4 2 cycloaddition reaction of c aryl Ketenimines with ptad as a synthetic equivalent of dinitrogen synthesis of triazolocinnolines and cinnolines
ChemInform, 2009Co-Authors: Mateo Alajarin, Angel Vidal, Baltasar Bonillo, Marta Marinluna, Raulangel OrenesAbstract:C,C,N-Triaryl Ketenimines and C-alkyl-C,N-diaryl Ketenimines react with 2 equiv of PTAD to provide 1,2,4-triazolo[1,2-a]cinnolines with a pendant triazolidindione group by means of a Diels-Alder/ene sequence. The treatment of such adducts with potassium hydroxide affords 3-aminocinnolines.
Angel Vidal - One of the best experts on this subject based on the ideXlab platform.
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recent highlights in Ketenimine chemistry
ChemInform, 2013Co-Authors: Mateo Alajarin, Marta Marinluna, Angel VidalAbstract:Selected recent developments in the chemistry of Ketenimines are presented, demonstrating that heterocumulenes of this class are versatile reactive intermediates in the synthesis of nitrogenated heterocycles. This microreview includes examples of intramolecular nucleophilic and radical additions, biradical cyclizations, 4π- and 6π-electrocyclic ring closures, [2+2], [3+2] and [4+2] cycloadditions, Ketenimine-to-nitrile rearrangements and 1,3-X, 1,5-X and 1,5-H shifts.
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tandem 1 5 hydride shift 6π electrocyclization of Ketenimines and carbodiimides substituted with cyclic acetal and dithioacetal functions experiments and computations
European Journal of Organic Chemistry, 2011Co-Authors: Mateo Alajarin, Mariamar Ortin, Baltasar Bonillo, Pilar Sanchezandrada, Angel VidalAbstract:N-Aryl Ketenimines bearing five- and six-membered cyclic acetal functions - such as 1,3-dioxolane, 1,3-dithiolane, 1,3-dioxane, and 1,3-dithiane systems - at the ortho position of the N-aryl substituent transform on mild thermal treatment into quinolines, through a tandem sequence consisting of a [1,5]-H shift followed by a 6π electrocyclic ring closure. Structurally analogous N-aryl carbodiimides are converted into quinazolines in comparable tandem processes. Similar sequences can be successfully applied to N-thienyl and N-pyrazolyl Ketenimines. DFT calculations have established a two-step mechanism for those conversions, consisting of an initial 1,5-hydride shift and subsequent 6π electrocyclization, and confirm the beneficial effect of the acetal function, which gives hydride character to the migrating hydrogen atom. The capability to promote the H shift depends on the type of acetal function (acetal better than dithioacetal), its ring size (five-membered better than six-membered) and the heterocumulenic fragment (Ketenimine better than carbodiimide). Changing the benzene ring connecting the acetal and Ketenimine functions for a heterocyclic ring has pronounced consequences for the magnitude of the energy barriers.
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domino reactions initiated by intramolecular hydride transfers from tri di arylmethane fragments to Ketenimine and carbodiimide functions
Organic and Biomolecular Chemistry, 2010Co-Authors: Mateo Alajarin, Angel Vidal, Mariamar Ortin, Baltasar Bonillo, Pilar Sanchezandrada, Raulangel OrenesAbstract:The ability of triarylmethane and diarylmethane fragments to behave as hydride donors participating in thermal [1,5]-H shift/6π-ERC tandem processes involving Ketenimine and carbodiimide functions is disclosed. C-Alkyl-C-phenyl Ketenimines N-substituted by a triarylmethane substructure convert into a variety of 3,3,4,4-tetrasubstituted-3,4-dihydroquinolines, as structurally related carbodiimides transform into 3,4,4-trisubstituted-3,4-dihydroquinazolines via transient ortho-azaxylylenes. The first step of these one-pot conversions, the [1,5]-H shift, is considered to be a hydride migration on the basis of the known hydricity of the tri(di)arylmethane fragment and the electrophilicity of the central heterocumulenic carbon atom, whereas the final electrocyclization involves the formation of a sterically congested C–C or C–N bond. In the cases of C,C-diphenyl substituted triarylmethane-Ketenimines the usual 6π-ERC becomes prohibited by the presence of two phenyl rings at each end of the azatrienic system. This situation opens new reaction channels: (a) following the initial hydride shift, the tandem sequence continues with an alternative electrocyclization mode to give 9,10-dihydroacridines, (b) the full sequence is initiated by a rare 1,5 migration of an electron-rich aryl group, followed by a 6π-ERC which leads to 2-aryl-3,4-dihydroquinolines, or (c) a different [1,5]-H shift/6π-ERC sequence involving the initial migration of a hydrogen atom from a methyl group at the ortho position to the nitrogen atom of the Ketenimine function. Diarylmethane-Ketenimines bearing a methyl group at the benzylic carbon atom experience a tandem double [1,5]-H shift, the first one being the usual benzylic hydride transfer whereas the second one involves the methyl group at the initial benzylic carbon atom, the reaction products being 2-aminostyrenes. Diarylmethane-Ketenimines lacking such a methyl group convert into 3,4-dihydroquinolines by the habitual tandem [1,5]-H shift/6π-ERC processes.
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tandem 1 5 hydride shift 1 5 s n cyclization with ethylene extrusion of 1 3 oxathiolane substituted Ketenimines and carbodiimines an experimental and computational study
ChemInform, 2010Co-Authors: Mateo Alajarin, Baltasar Bonillo, Pilar Sanchezandrada, Angel VidalAbstract:Upon heating Ketenimines of type (III) and carbodiimines derived from isocyanates (VIII) undergo unexpected transformation into benzisothiazolones via 1,5-hydride shift, 1,5-electrocyclization, and [3 + 2] cycloreversion.
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4 2 cycloaddition reaction of c aryl Ketenimines with ptad as a synthetic equivalent of dinitrogen synthesis of triazolocinnolines and cinnolines
ChemInform, 2009Co-Authors: Mateo Alajarin, Angel Vidal, Baltasar Bonillo, Marta Marinluna, Raulangel OrenesAbstract:C,C,N-Triaryl Ketenimines and C-alkyl-C,N-diaryl Ketenimines react with 2 equiv of PTAD to provide 1,2,4-triazolo[1,2-a]cinnolines with a pendant triazolidindione group by means of a Diels-Alder/ene sequence. The treatment of such adducts with potassium hydroxide affords 3-aminocinnolines.
Kasi Pitchumani - One of the best experts on this subject based on the ideXlab platform.
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Copper(I)-Catalyzed Three Component Reaction of Sulfonyl Azide, Alkyne, and Nitrone Cycloaddition/Rearrangement Cascades: A Novel One-Step Synthesis of Imidazolidin-4-ones
2016Co-Authors: Kayambu Namitharan, Kasi PitchumaniAbstract:A novel one-pot azide–alkyne/Ketenimine–nitrone cycloaddition sequence that is induced by copper(I) and allows the transformation of sulfonyl azides, alkynes, and nitrones to highly substituted imidazolidin-4-ones is described. The corresponding heterogeneous version utilizing Cu(I)-modified zeolites as recyclable heterogeneous catalysts shows marginally improved yield and diastereoselectivity
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copper i y zeolite catalyzed regio and stereoselective 2 2 2 cyclotrimerization cascade an atom and step economical synthesis of pyrimido 1 6 a quinoline
Journal of Organic Chemistry, 2015Co-Authors: Devenderan Ramanathan, Kasi PitchumaniAbstract:An elegant copper(I)-Y zeolite-catalyzed tandem process, involving Ketenimine-based termolecular [2 + 2 + 2]/[NC + CC + NC] cycloaddition, using sulfonyl azide, alkyne, and quinoline, to prepare pyrimido[1,6-a]quinolines is reported. In this straightforward, highly atom- and step-economical protocol, copper(I) promotes for azide-alkyne [3 + 2] cycloaddition which is followed by ring-rearrangement/Ketenimine formation/regio- and stereoselective [2 + 2 + 2] termolecular cycloaddition and dehydrogenation cascade to yield selectively the E-isomer of pyrimido[1,6-a]quinoline.
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Copper(I)-Catalyzed One-Pot Synthesis of Highly Functionalized Pyrrolidines from Sulfonyl Azides, Alkynes, and Dimethyl 2-(Phenylamino)maleate.
ChemInform, 2015Co-Authors: Devenderan Ramanathan, Kasi PitchumaniAbstract:This cascade reaction consists of an azide—alkyne [3 + 2] cycloaddition/ring rearrangement, Ketenimine formation, an intermolecular nucleophilic addition sequence and subsequent intramolecular cyclization followed by [1,3]-H shift.
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Copper(I)‑Y Zeolite-Catalyzed Regio- and Stereoselective [2 + 2 + 2] Cyclotrimerization Cascade: An Atom- and Step-Economical Synthesis of Pyrimido[1,6‑a]quinoline
2015Co-Authors: Devenderan Ramanathan, Kasi PitchumaniAbstract:An elegant copper(I)-Y zeolite-catalyzed tandem process, involving Ketenimine-based termolecular [2 + 2 + 2]/[NC + CC + NC] cycloaddition, using sulfonyl azide, alkyne, and quinoline, to prepare pyrimido[1,6-a]quinolines is reported. In this straightforward, highly atom- and step-economical protocol, copper(I) promotes for azide–alkyne [3 + 2] cycloaddition which is followed by ring-rearrangement/Ketenimine formation/regio- and stereoselective [2 + 2 + 2] termolecular cycloaddition and dehydrogenation cascade to yield selectively the E-isomer of pyrimido[1,6-a]quinoline
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copper i catalyzed one pot synthesis of highly functionalized pyrrolidines from sulfonyl azides alkynes and dimethyl 2 phenylamino maleate
European Journal of Organic Chemistry, 2015Co-Authors: Devenderan Ramanathan, Kasi PitchumaniAbstract:An efficient one-pot synthesis of highly functionalized pyrrolidines by using sulfonyl azides, alkynes, and dimethyl 2-(phenylamino)maleate catalyzed by copper(I)–Y zeolite under mild reaction conditions was investigated. This cascade process involves an azide–alkyne [3+2] cycloaddition/ring rearrangement/Ketenimine formation/intermolecular nucleophilic addition cascade and consequent intramolecular cyclization followed by [1,3]-H shift. The important advantage of this methodology, which allows selective intramolecular nucleophilic attack of the generated Ketenimine carbanion on an ester moiety for the first time, is that the starting materials can be easily prepared.
Huadong Xua - One of the best experts on this subject based on the ideXlab platform.
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stereoselective construction of bridged trans aza bicyclo 7 6 3 2 1 alkenyl imines through ring expansion aza cope rearrangement
Organic Letters, 2015Co-Authors: Mei-hua Shen, Chuhan Sun, Huadong XuaAbstract:A highly stereoselective method for efficient synthesis of unprecedented bridged bicyclo[7/6,3/2,1]alkenyl amidines is described using cyclic N-allyl-aminoalkyne as a substrate. A Ketenimine formation/cyclization/aza-Cope rearrangement cascade proceeds either with or without the aid of external DIPEA depending on substrate basicity. Fused bicycloamidines are also obtained via the same protocol using different N-allyl cyclic aminoalkynes.
Pinaki Talukdar - One of the best experts on this subject based on the ideXlab platform.
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a 1 3 amino group migration route to form acrylamidines
ChemInform, 2014Co-Authors: Dinesh Pratapsinh Chauhan, Sreejith Jayasree Varma, Arjun Vijeta, Pallavi Banerjee, Pinaki TalukdarAbstract:A novel route for the synthesis of acrylamidines by Cu-catalyzed addition of tosylazide to 1-aminopropines and subsequent intramolecular addition of nucleophiles to Ketenimines with 1,3-amino group migration is presented.
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a 1 3 amino group migration route to form acrylamidines
Chemical Communications, 2014Co-Authors: Dinesh Pratapsinh Chauhan, Sreejith Jayasree Varma, Arjun Vijeta, Pallavi Banerjee, Pinaki TalukdarAbstract:A novel 1,3-amino group migration strategy for the synthesis of acrylamidines is presented. Cu(I) catalyzed reaction of N,N-disubstituted propargylamine with tosylazide generates a highly reactive Ketenimine intermediate which is trapped by a tethered amino group leading to the rearrangement reaction.
