The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Koichi Mikami - One of the best experts on this subject based on the ideXlab platform.
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Catalytic Asymmetric Synthesis of Stable Oxetenes via Lewis Acid-Promoted [2 + 2] Cycloaddition
2016Co-Authors: Kohsuke Aikawa, Natsumi Shimizu, Yu̅ta Hioki, Koichi MikamiAbstract:A highly enantioselective and atom-economical [2 + 2] cycloaddition of various alkynes with trifluoropyruvate using a dicationic (S)-BINAP–Pd catalyst has been established. This is the first enantioselective synthesis of stable Oxetene derivatives, whose structure has been clarified by X-ray analysis. This catalytic process offers a practical synthetic method for Oxetene derivatives (catalyst loading: up to 0.1 mol %), which can serve as novel chiral building blocks for pharmaceuticals and agrochemicals and can also be transformed into a variety of enantiomerically enriched CF3-substituted compounds with high stereoselectivity
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Effect of the trifluoromethyl group on torquoselectivity in the 4π ring-opening reaction of Oxetenes: stereoselective synthesis of tetrasubstituted olefins
Chem. Sci., 2014Co-Authors: Kohsuke Aikawa, Natsumi Shimizu, Kazuya Honda, Yuta Hioki, Koichi MikamiAbstract:A highly stereoselective synthesis of tetrasubstituted olefins bearing a trifluoromethyl group via the thermal 4π electrocyclic ring-opening reaction of Oxetenes, simply prepared by the Pd-catalyzed [2+2] cycloaddition reaction of various alkynes with trifluoropyruvate, is achieved. In this reaction process, the trifluoromethyl group prefers inward rotational torquoselectivity because of the orbital interactions between the breaking C–O σ orbital on the Oxetene moiety and the C–F σ* orbital in the transition state.
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Catalytic asymmetric synthesis of stable Oxetenes via Lewis acid-promoted [2+2] cycloaddition.
Journal of the American Chemical Society, 2011Co-Authors: Kohsuke Aikawa, Natsumi Shimizu, Yuta Hioki, Koichi MikamiAbstract:A highly enantioselective and atom-economical [2 + 2] cycloaddition of various alkynes with trifluoropyruvate using a dicationic (S)-BINAP–Pd catalyst has been established. This is the first enantioselective synthesis of stable Oxetene derivatives, whose structure has been clarified by X-ray analysis. This catalytic process offers a practical synthetic method for Oxetene derivatives (catalyst loading: up to 0.1 mol %), which can serve as novel chiral building blocks for pharmaceuticals and agrochemicals and can also be transformed into a variety of enantiomerically enriched CF3-substituted compounds with high stereoselectivity.
Kohsuke Aikawa - One of the best experts on this subject based on the ideXlab platform.
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Catalytic Asymmetric Synthesis of Stable Oxetenes via Lewis Acid-Promoted [2 + 2] Cycloaddition
2016Co-Authors: Kohsuke Aikawa, Natsumi Shimizu, Yu̅ta Hioki, Koichi MikamiAbstract:A highly enantioselective and atom-economical [2 + 2] cycloaddition of various alkynes with trifluoropyruvate using a dicationic (S)-BINAP–Pd catalyst has been established. This is the first enantioselective synthesis of stable Oxetene derivatives, whose structure has been clarified by X-ray analysis. This catalytic process offers a practical synthetic method for Oxetene derivatives (catalyst loading: up to 0.1 mol %), which can serve as novel chiral building blocks for pharmaceuticals and agrochemicals and can also be transformed into a variety of enantiomerically enriched CF3-substituted compounds with high stereoselectivity
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Effect of the trifluoromethyl group on torquoselectivity in the 4π ring-opening reaction of Oxetenes: stereoselective synthesis of tetrasubstituted olefins
Chem. Sci., 2014Co-Authors: Kohsuke Aikawa, Natsumi Shimizu, Kazuya Honda, Yuta Hioki, Koichi MikamiAbstract:A highly stereoselective synthesis of tetrasubstituted olefins bearing a trifluoromethyl group via the thermal 4π electrocyclic ring-opening reaction of Oxetenes, simply prepared by the Pd-catalyzed [2+2] cycloaddition reaction of various alkynes with trifluoropyruvate, is achieved. In this reaction process, the trifluoromethyl group prefers inward rotational torquoselectivity because of the orbital interactions between the breaking C–O σ orbital on the Oxetene moiety and the C–F σ* orbital in the transition state.
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Catalytic asymmetric synthesis of stable Oxetenes via Lewis acid-promoted [2+2] cycloaddition.
Journal of the American Chemical Society, 2011Co-Authors: Kohsuke Aikawa, Natsumi Shimizu, Yuta Hioki, Koichi MikamiAbstract:A highly enantioselective and atom-economical [2 + 2] cycloaddition of various alkynes with trifluoropyruvate using a dicationic (S)-BINAP–Pd catalyst has been established. This is the first enantioselective synthesis of stable Oxetene derivatives, whose structure has been clarified by X-ray analysis. This catalytic process offers a practical synthetic method for Oxetene derivatives (catalyst loading: up to 0.1 mol %), which can serve as novel chiral building blocks for pharmaceuticals and agrochemicals and can also be transformed into a variety of enantiomerically enriched CF3-substituted compounds with high stereoselectivity.
James A Bull - One of the best experts on this subject based on the ideXlab platform.
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oxetane ethers are formed reversibly in the lithium catalyzed friedel crafts alkylation of phenols with oxetanols synthesis of dihydrobenzofurans diaryloxetanes and oxetane ethers
Tetrahedron, 2018Co-Authors: Rosemary A Croft, Chulho Choi, James J Mousseau, James A BullAbstract:Abstract Studies on the mechanism and intermediate products in the Friedel–Crafts reaction between oxetanols and phenols are presented. The formation of O-alkylated intermediates is identified using 1H NMR spectroscopy, in a reversible formation of the kinetic oxetane ether products. An interesting relationship between the electronic nature of the nucleophile and the degree of O-alkylation is uncovered. For phenols substituted with an electron withdrawing group such as CN, oxetane ethers are the only products isolated regardless of reaction time. Increasing the electron rich nature of the phenol leads to an increased proportion of the thermodynamic C-alkylated Friedel–Crafts products after just 1 h and as the sole product/s after extended reaction times. These studies have enabled a more complete catalytic cycle to be proposed. Using the same lithium catalyst and carefully selected reaction times, several examples of oxetane ethers are successfully isolated as novel bioisosteres for ester groups.
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lithium catalyzed thiol alkylation with tertiary and secondary alcohols synthesis of 3 sulfanyl oxetanes as bioisosteres
Chemistry: A European Journal, 2018Co-Authors: Rosemary A Croft, Chulho Choi, James J Mousseau, James A BullAbstract:: 3-Sulfanyl-oxetanes are presented as promising novel bioisosteric replacements for thioesters or benzyl sulfides. From oxetan-3-ols, a mild and inexpensive Li catalyst enables chemoselective C-OH activation and thiol alkylation. Oxetane sulfides are formed from various thiols providing novel motifs in new chemical space and specifically as bioisosteres for thioesters due to their similar shape and electronic properties. Under the same conditions, various π-activated secondary and tertiary alcohols are also successful. Derivatization of the oxetane sulfide linker provides further novel oxetane classes and building blocks. Comparisons of key physicochemical properties of the oxetane compounds to selected carbonyl and methylene analogues indicate that these motifs are suitable for incorporation into drug discovery efforts.
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oxetanes recent advances in synthesis reactivity and medicinal chemistry
Chemical Reviews, 2016Co-Authors: James A Bull, Owen A Davis, Rosemary A Croft, Robert Doran, Kate F MorganAbstract:The four-membered oxetane ring has been increasingly exploited for its contrasting behaviors: its influence on physicochemical properties as a stable motif in medicinal chemistry and its propensity to undergo ring-opening reactions as a synthetic intermediate. These applications have driven numerous studies into the synthesis of new oxetane derivatives. This review takes an overview of the literature for the synthesis of oxetane derivatives, concentrating on advances in the last five years up to the end of 2015. These methods are clustered by strategies for preparation of the ring and further derivatization of preformed oxetane-containing building blocks. Examples of the use of oxetanes in medicinal chemistry are reported, including a collation of oxetane derivatives appearing in recent patents for medicinal chemistry applications. Finally, examples of oxetane derivatives in ring-opening and ring-expansion reactions are described.
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synthesis of diversely functionalised 2 2 disubstituted oxetanes fragment motifs in new chemical space
Chemical Communications, 2015Co-Authors: Owen A Davis, Rosemary A Croft, James A BullAbstract:Di-, tri- and tetra-substituted oxetane derivatives with combinations of ester, amide, nitrile, aryl, sulfone and phosphonate substituents are prepared as fragments or building blocks for drug discovery. The synthesis of these novel oxetane functional groups, in new chemical space, is achieved via rhodium-catalysed O–H insertion and C–C bond forming cyclisation.
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synthesis of di tri and tetrasubstituted oxetanes by rhodium catalyzed oh insertion and cc bond forming cyclization
Angewandte Chemie, 2014Co-Authors: Owen A Davis, James A BullAbstract:Oxetanes offer exciting potential as structural motifs and intermediates in drug discovery and materials science. Here an efficient strategy for the synthesis of oxetane rings incorporating pendant functional groups is described. A wide variety of oxetane 2,2-dicarboxylates were accessed in high yields, including functionalized 3-/4-aryl- and alkyl-substituted oxetanes and fused oxetane bicycles. Enantioenriched alcohols provided enantioenriched oxetanes with complete retention of configuration. The oxetane products were further derivatized, while the ring was maintained intact, thus highlighting their potential as building blocks for medicinal chemistry.
Natsumi Shimizu - One of the best experts on this subject based on the ideXlab platform.
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Catalytic Asymmetric Synthesis of Stable Oxetenes via Lewis Acid-Promoted [2 + 2] Cycloaddition
2016Co-Authors: Kohsuke Aikawa, Natsumi Shimizu, Yu̅ta Hioki, Koichi MikamiAbstract:A highly enantioselective and atom-economical [2 + 2] cycloaddition of various alkynes with trifluoropyruvate using a dicationic (S)-BINAP–Pd catalyst has been established. This is the first enantioselective synthesis of stable Oxetene derivatives, whose structure has been clarified by X-ray analysis. This catalytic process offers a practical synthetic method for Oxetene derivatives (catalyst loading: up to 0.1 mol %), which can serve as novel chiral building blocks for pharmaceuticals and agrochemicals and can also be transformed into a variety of enantiomerically enriched CF3-substituted compounds with high stereoselectivity
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Effect of the trifluoromethyl group on torquoselectivity in the 4π ring-opening reaction of Oxetenes: stereoselective synthesis of tetrasubstituted olefins
Chem. Sci., 2014Co-Authors: Kohsuke Aikawa, Natsumi Shimizu, Kazuya Honda, Yuta Hioki, Koichi MikamiAbstract:A highly stereoselective synthesis of tetrasubstituted olefins bearing a trifluoromethyl group via the thermal 4π electrocyclic ring-opening reaction of Oxetenes, simply prepared by the Pd-catalyzed [2+2] cycloaddition reaction of various alkynes with trifluoropyruvate, is achieved. In this reaction process, the trifluoromethyl group prefers inward rotational torquoselectivity because of the orbital interactions between the breaking C–O σ orbital on the Oxetene moiety and the C–F σ* orbital in the transition state.
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Catalytic asymmetric synthesis of stable Oxetenes via Lewis acid-promoted [2+2] cycloaddition.
Journal of the American Chemical Society, 2011Co-Authors: Kohsuke Aikawa, Natsumi Shimizu, Yuta Hioki, Koichi MikamiAbstract:A highly enantioselective and atom-economical [2 + 2] cycloaddition of various alkynes with trifluoropyruvate using a dicationic (S)-BINAP–Pd catalyst has been established. This is the first enantioselective synthesis of stable Oxetene derivatives, whose structure has been clarified by X-ray analysis. This catalytic process offers a practical synthetic method for Oxetene derivatives (catalyst loading: up to 0.1 mol %), which can serve as novel chiral building blocks for pharmaceuticals and agrochemicals and can also be transformed into a variety of enantiomerically enriched CF3-substituted compounds with high stereoselectivity.
Xiangjun Chen - One of the best experts on this subject based on the ideXlab platform.
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vibrational effects on electron momentum distributions of outer valence orbitals of oxetane
Journal of Physical Chemistry A, 2016Co-Authors: Yaguo Tang, X Y Shan, Jing Yang, Zhe Zhang, Noboru Watanabe, Masakazu Yamazaki, Masahiko Takahashi, Xiangjun ChenAbstract:Vibrational effects on electron momentum distributions (EMDs) of outer-valence orbitals of oxetane are computed with a comprehensive consideration of all vibrational modes. It is found that vibrational motions influence EMDs of all outer-valence orbitals noticeably. The agreement between theoretical and experimental momentum profiles of the first five orbitals is greatly improved when including molecular vibrations in the calculation. In particular, the large turn-up at low momentum in the experimental momentum profile of the 3b1 orbital is well interpreted by vibrational effects, indicating that, besides the low-frequency ring-puckering mode, C–H stretching motion also plays a significant role in affecting EMDs of outer-valence orbitals of oxetane. The case of oxetane exhibits the significance of checking vibrational effects when performing electron momentum spectroscopy measurements.
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vibrational effects on electron momentum distributions of outer valence orbitals of oxetane
Journal of Physical Chemistry A, 2016Co-Authors: Yaguo Tang, X Y Shan, Jing Yang, Noboru Watanabe, Masakazu Yamazaki, Masahiko Takahashi, Shanshan Niu, Z P Zhang, Xiangjun ChenAbstract:Vibrational effects on electron momentum distributions (EMDs) of outer-valence orbitals of oxetane are computed with a comprehensive consideration of all vibrational modes. It is found that vibrational motions influence EMDs of all outer-valence orbitals noticeably. The agreement between theoretical and experimental momentum profiles of the first five orbitals is greatly improved when including molecular vibrations in the calculation. In particular, the large turn-up at low momentum in the experimental momentum profile of the 3b1 orbital is well interpreted by vibrational effects, indicating that, besides the low-frequency ring-puckering mode, C–H stretching motion also plays a significant role in affecting EMDs of outer-valence orbitals of oxetane. The case of oxetane exhibits the significance of checking vibrational effects when performing electron momentum spectroscopy measurements.
