The Experts below are selected from a list of 168 Experts worldwide ranked by ideXlab platform
Shigeyasu Kuroda - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and Stability of 1,1-Diphenyl-1 H -azulenium Cation
2016Co-Authors: Mitsunori Oda, Ryuta Miyatake, Nobue Nakajima, Yoshimitsu Kumai, Akira Ohta, Shigeyasu KurodaAbstract:In three steps by aldol condensation with benzaldehyde, conjugate addition of lithium diphenylcuprate and subsequent oxidation, 1-acetylcyclohepta-1,3,5-triene (10) was transformed into 1-(3,3-diphenylacryloly) -cyclohepta-1,3,5-triene (11). The title cation 9 was synthesized from 11 by a sequence involving Nazarov cyclization, Shapiro Reaction and final hydride abstraction with trityl perchlorate. The pKR+ value was determined to be 6.4, which is less than that of the analogous fluorenyl cation 8. Upon heating 9 rearranges to yield 1,2-diphenylazulene (22), quantitatively.
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Synthesis, Stability, and Crystal Structure of an Azulenium Cation Containing an Adamantyl Group
European Journal of Organic Chemistry, 2008Co-Authors: Mitsunori Oda, Ryuta Miyatake, Nobue Nakajima, Nguyen Chung Thanh, Kazuhiro Kitahara, Shigeyasu KurodaAbstract:Starting from the trimethylsilyl enol ether of 1-acetyl-1,3,5-cycloheptatriene, the title 1H-azulenium cation was synthesized by a five-step sequence that involved a Noyori–Mukaiyama aldol Reaction, a Nazarov cyclization, a Shapiro Reaction, and a hydride abstraction. The Nazarov Reaction of the aldol-type adduct resulted in the formation of an unusual double-bond position isomer, which has never been obtained in similar Reactions forming tetrahydroazulenones. The pKR+ value of the title cation was found to be 9.8, which is less than that expected by inductive stabilization from the number of carbons at the 1-position. The X-ray crystal structure of the title cation (ClO4– salt) reveals CH–O interactions and deformation of the azulenyl ion part.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
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Dispiro[cyclohexane-1,1′-(1′,7′-dihydrocyclopenta[f]azulenium)-7′,1′′-cyclohexane] perchlorate, a new highly stable hydrocarbon cation
Tetrahedron Letters, 2002Co-Authors: Mitsunori Oda, Hitoshi Kainuma, Ryuta Miyatake, Shigeyasu KurodaAbstract:Abstract The title cation was synthesized from 1,6-diacetylcyclohepta-1,3,5-triene by a six-step sequence involving an aldol Reaction, the Nazarov cyclization, the Shapiro Reaction and hydride abstraction, and its p K R+ value was found to be 13.2, providing a new access to highly stable hydrocarbon cations.
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Synthesis, Stability, and X-Ray Crystallographic Structure Analysis of Spiro[1H-azulenium-1,1′-cycloalkane] Ions
Tetrahedron, 2000Co-Authors: Mitsunori Oda, Hitoshi Kainuma, Ryuta Miyatake, Aya Fukuta, Takanori Kajioka, Takuya Uchiyama, Shigeyasu KurodaAbstract:Abstract Direct cycloalkylation of 1,6-dihydroazulene and subsequent hydride abstraction with a trityl salt gave spiro[1H-azulenium-1,1′-cyclopentane and -1,1′-cyclohexane] ions (3 and 4). On the other hand, spiro[1H-azulenium-1,1′-cycloheptane] ion (5) was synthesized from 1-acetylcyclohepta-1,3,5-triene by a sequence involving the Mukaiyama aldol Reaction, the Nazarov cyclization, the Shapiro Reaction, and hydride abstraction. These cations showed greater kinetic stability than the three- and four-membered ring homologues. Their pKR+ values are far greater compared with those of the known disubstituted tropylium cations and are in the order of the number of carbon atoms at the 1 position, indicating that an inductive effect of the spiroalkyl groups, besides the π-conjugative and σ-conjugative effects, governs the thermodynamic stability. X-Ray crystallographic structure analysis of these cations was also described.
Diego Sampedro - One of the best experts on this subject based on the ideXlab platform.
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On the mechanism of the Shapiro Reaction: understanding the regioselectivity
RSC Advances, 2015Co-Authors: Ignacio Funes-ardoiz, Raúl Losantos, Diego SampedroAbstract:A detailed DFT-level mechanism elucidation of the two-step Reaction of tosylhydrazones with alkyllithium reagents (the Shapiro Reaction) is presented. A rationale of the experimental regioselectivity is offered together with some suggestions for modifying the experimental main regioisomer. Also, the proposed general mechanism was checked with a recent modification of the Shapiro Reaction involving a fluorination Reaction.
Bryan E. Roberts - One of the best experts on this subject based on the ideXlab platform.
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THE APPLICATION OF A Shapiro Reaction - SUZUKI COUPLING SEQUENCE TO THE STEREOSELECTIVE SYNTHESIS OF E-TRISUBSTITUTED OLEFINS
Tetrahedron Letters, 1997Co-Authors: E. J. Corey, Bryan E. RobertsAbstract:Abstract A three-component coupling process is described for the rapid, stereoselective synthesis of a wide variety of E-trisubstituted olefins.
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THE APPLICATION OF THE Shapiro Reaction TO THE STEREOSELECTIVE SYNTHESIS OF E-TRISUBSTITUTED OLEFINS FOR CATION-OLEFIN CYCLIZATION BY THREE COMPONENT COUPLING
Tetrahedron Letters, 1997Co-Authors: E. J. Corey, Jaemoon Lee, Bryan E. RobertsAbstract:Abstract A method is described for the rapid and stereoselective assembly of E-trisubstituted olefins by a convergent process from three components
Mitsunori Oda - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and Stability of 1,1-Diphenyl-1 H -azulenium Cation
2016Co-Authors: Mitsunori Oda, Ryuta Miyatake, Nobue Nakajima, Yoshimitsu Kumai, Akira Ohta, Shigeyasu KurodaAbstract:In three steps by aldol condensation with benzaldehyde, conjugate addition of lithium diphenylcuprate and subsequent oxidation, 1-acetylcyclohepta-1,3,5-triene (10) was transformed into 1-(3,3-diphenylacryloly) -cyclohepta-1,3,5-triene (11). The title cation 9 was synthesized from 11 by a sequence involving Nazarov cyclization, Shapiro Reaction and final hydride abstraction with trityl perchlorate. The pKR+ value was determined to be 6.4, which is less than that of the analogous fluorenyl cation 8. Upon heating 9 rearranges to yield 1,2-diphenylazulene (22), quantitatively.
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Synthesis, Stability, and Crystal Structure of an Azulenium Cation Containing an Adamantyl Group
European Journal of Organic Chemistry, 2008Co-Authors: Mitsunori Oda, Ryuta Miyatake, Nobue Nakajima, Nguyen Chung Thanh, Kazuhiro Kitahara, Shigeyasu KurodaAbstract:Starting from the trimethylsilyl enol ether of 1-acetyl-1,3,5-cycloheptatriene, the title 1H-azulenium cation was synthesized by a five-step sequence that involved a Noyori–Mukaiyama aldol Reaction, a Nazarov cyclization, a Shapiro Reaction, and a hydride abstraction. The Nazarov Reaction of the aldol-type adduct resulted in the formation of an unusual double-bond position isomer, which has never been obtained in similar Reactions forming tetrahydroazulenones. The pKR+ value of the title cation was found to be 9.8, which is less than that expected by inductive stabilization from the number of carbons at the 1-position. The X-ray crystal structure of the title cation (ClO4– salt) reveals CH–O interactions and deformation of the azulenyl ion part.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
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Dispiro[cyclohexane-1,1′-(1′,7′-dihydrocyclopenta[f]azulenium)-7′,1′′-cyclohexane] perchlorate, a new highly stable hydrocarbon cation
Tetrahedron Letters, 2002Co-Authors: Mitsunori Oda, Hitoshi Kainuma, Ryuta Miyatake, Shigeyasu KurodaAbstract:Abstract The title cation was synthesized from 1,6-diacetylcyclohepta-1,3,5-triene by a six-step sequence involving an aldol Reaction, the Nazarov cyclization, the Shapiro Reaction and hydride abstraction, and its p K R+ value was found to be 13.2, providing a new access to highly stable hydrocarbon cations.
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Synthesis, Stability, and X-Ray Crystallographic Structure Analysis of Spiro[1H-azulenium-1,1′-cycloalkane] Ions
Tetrahedron, 2000Co-Authors: Mitsunori Oda, Hitoshi Kainuma, Ryuta Miyatake, Aya Fukuta, Takanori Kajioka, Takuya Uchiyama, Shigeyasu KurodaAbstract:Abstract Direct cycloalkylation of 1,6-dihydroazulene and subsequent hydride abstraction with a trityl salt gave spiro[1H-azulenium-1,1′-cyclopentane and -1,1′-cyclohexane] ions (3 and 4). On the other hand, spiro[1H-azulenium-1,1′-cycloheptane] ion (5) was synthesized from 1-acetylcyclohepta-1,3,5-triene by a sequence involving the Mukaiyama aldol Reaction, the Nazarov cyclization, the Shapiro Reaction, and hydride abstraction. These cations showed greater kinetic stability than the three- and four-membered ring homologues. Their pKR+ values are far greater compared with those of the known disubstituted tropylium cations and are in the order of the number of carbon atoms at the 1 position, indicating that an inductive effect of the spiroalkyl groups, besides the π-conjugative and σ-conjugative effects, governs the thermodynamic stability. X-Ray crystallographic structure analysis of these cations was also described.
Ignacio Funes-ardoiz - One of the best experts on this subject based on the ideXlab platform.
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On the mechanism of the Shapiro Reaction: understanding the regioselectivity
RSC Advances, 2015Co-Authors: Ignacio Funes-ardoiz, Raúl Losantos, Diego SampedroAbstract:A detailed DFT-level mechanism elucidation of the two-step Reaction of tosylhydrazones with alkyllithium reagents (the Shapiro Reaction) is presented. A rationale of the experimental regioselectivity is offered together with some suggestions for modifying the experimental main regioisomer. Also, the proposed general mechanism was checked with a recent modification of the Shapiro Reaction involving a fluorination Reaction.