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Yoo Tanabe - One of the best experts on this subject based on the ideXlab platform.
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Dehydration‐type Ti‐Claisen Condensation (Carbonhomologation) of α‐Heteroatom‐substituted Acetates with Alkyl Formates: Utilization as (Z)‐Stereodefined Cross‐coupling Partners and Application to Concise Synthesis of Strobilurin A
Advanced Synthesis & Catalysis, 2017Co-Authors: Hidefumi Nakatsuji, Risa Kamada, Hideya Kitaguchi, Yoo TanabeAbstract:Abstract. TiCl4–Et3N or –Bu3N reagent conducted a highly (Z)-stereoselective carbon homologation (dehydration type Ti-Claisen Condensation) of alkyl α-heteroatom (halo and sulfonyloxy)-substituted acetates (XCH2CO2R) with alkyl formates (HCO2R) to afford various alkyl β-alkoxy-α-halo or sulfonyloxy-substituted acrylates (24 examples; 51%–91% yield). Stereoretentive Suzuki-Miyaura, Negishi, and Sonogashira cross-couplings using the obtained methyl β-methoxy-α-halo or sulfonyloxy-substituted acrylates proceeded smoothly to produce a variety of β-alkoxy-α-substituted acrylates in moderate to high yield (35 examples; 29% – 99% yield). As a successful application, a 3-step straightforward synthesis of strobilurin A was performed utilizing the present reaction sequence (dehydration type Ti-Claisen Condensation and Suzuki-Miyaura cross-coupling), wherein the geometry of the three consecutive olefins (2E,3Z,5E) was completely maintained.
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Asymmetric Total Synthesis of (–)‐Azaspirene by Utilizing Ti‐Claisen Condensation and Ti‐Direct Aldol Reaction
European Journal of Organic Chemistry, 2016Co-Authors: Mikiko Sugi, Tomonori Misaki, Ryohei Nagase, Hidefumi Nakatsuji, Yoo TanabeAbstract:A successful asymmetric total synthesis of (–)-azaspirene has been accomplished by utilizing (3R)-6-cinnamyl-3-methyl-3-phenyl-1,4-dioxane-2,5-dione, a readily accessible chiral template. The present method involves two distinctive TiCl4/amine-mediated reactions: (i) an asymmetric Ti-crossed-Claisen Condensation of the chiral template with propanoyl chloride followed by methanolysis to afford methyl (2R)-(4E)-2-hydroxy-5-phenyl-2-propanoylpent-4-enoate, the key chiral synthon and (ii) a robust Ti-direct aldol addition reaction, instead of the reported lithium diisopropylamide/hexamethylphosphorictriamide (LDA/HMPA) or potassium hexamethyldisilazide (KHMDS)-mediated reaction, by using the trimethylsilyl (TMS) ether of α-acyl-γ-lactam to successfully furnish the new aldol adduct. Final oxidation, cyclization, and tert-butyldimethylsilyl (TBS) removal produced (–)-azaspirene from the key template in 23 steps (total yield 1.7 %).
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asymmetric total synthesis of azaspirene by utilizing ti Claisen Condensation and ti direct aldol reaction
European Journal of Organic Chemistry, 2016Co-Authors: Mikiko Sugi, Tomonori Misaki, Ryohei Nagase, Hidefumi Nakatsuji, Yoo TanabeAbstract:A successful asymmetric total synthesis of (–)-azaspirene has been accomplished by utilizing (3R)-6-cinnamyl-3-methyl-3-phenyl-1,4-dioxane-2,5-dione, a readily accessible chiral template. The present method involves two distinctive TiCl4/amine-mediated reactions: (i) an asymmetric Ti-crossed-Claisen Condensation of the chiral template with propanoyl chloride followed by methanolysis to afford methyl (2R)-(4E)-2-hydroxy-5-phenyl-2-propanoylpent-4-enoate, the key chiral synthon and (ii) a robust Ti-direct aldol addition reaction, instead of the reported lithium diisopropylamide/hexamethylphosphorictriamide (LDA/HMPA) or potassium hexamethyldisilazide (KHMDS)-mediated reaction, by using the trimethylsilyl (TMS) ether of α-acyl-γ-lactam to successfully furnish the new aldol adduct. Final oxidation, cyclization, and tert-butyldimethylsilyl (TBS) removal produced (–)-azaspirene from the key template in 23 steps (total yield 1.7 %).
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Asymmetric Ti-crossed Claisen Condensation: application to concise asymmetric total synthesis of alternaric acid.
Chemical communications (Cambridge England), 2013Co-Authors: Ryohei Nagase, Tomonori Misaki, Yumiko Oguni, Satoko Ureshino, Hiroaki Mura, Yoo TanabeAbstract:Asymmetric Ti-crossed Claisen Condensation utilizing the dioxane-2,5-dione chiral template and its successful application to total synthesis of chiral alternaric acid are described.
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first sequential mukaiyama michael reaction crossed Claisen Condensation using two molar ketene silyl acetals and one molar α β unsaturated esters promoted by a naoh catalyst
ChemInform, 2010Co-Authors: Hiroaki Tamagaki, Ryohei Nagase, Yuuya Nawate, Yoo TanabeAbstract:A sequential Mukaiyama—Michael reaction and regioselective crossed-Claisen Condensation to afford 1,3,7-tricarbonyl scaffolds is developed using two equivalents of ketene silyl acetals (II)/(IV) and one equivalent α,β-unsaturated esters (I) in either a stepwise or one-pot procedure.
Tomonori Misaki - One of the best experts on this subject based on the ideXlab platform.
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Asymmetric Total Synthesis of (–)‐Azaspirene by Utilizing Ti‐Claisen Condensation and Ti‐Direct Aldol Reaction
European Journal of Organic Chemistry, 2016Co-Authors: Mikiko Sugi, Tomonori Misaki, Ryohei Nagase, Hidefumi Nakatsuji, Yoo TanabeAbstract:A successful asymmetric total synthesis of (–)-azaspirene has been accomplished by utilizing (3R)-6-cinnamyl-3-methyl-3-phenyl-1,4-dioxane-2,5-dione, a readily accessible chiral template. The present method involves two distinctive TiCl4/amine-mediated reactions: (i) an asymmetric Ti-crossed-Claisen Condensation of the chiral template with propanoyl chloride followed by methanolysis to afford methyl (2R)-(4E)-2-hydroxy-5-phenyl-2-propanoylpent-4-enoate, the key chiral synthon and (ii) a robust Ti-direct aldol addition reaction, instead of the reported lithium diisopropylamide/hexamethylphosphorictriamide (LDA/HMPA) or potassium hexamethyldisilazide (KHMDS)-mediated reaction, by using the trimethylsilyl (TMS) ether of α-acyl-γ-lactam to successfully furnish the new aldol adduct. Final oxidation, cyclization, and tert-butyldimethylsilyl (TBS) removal produced (–)-azaspirene from the key template in 23 steps (total yield 1.7 %).
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asymmetric total synthesis of azaspirene by utilizing ti Claisen Condensation and ti direct aldol reaction
European Journal of Organic Chemistry, 2016Co-Authors: Mikiko Sugi, Tomonori Misaki, Ryohei Nagase, Hidefumi Nakatsuji, Yoo TanabeAbstract:A successful asymmetric total synthesis of (–)-azaspirene has been accomplished by utilizing (3R)-6-cinnamyl-3-methyl-3-phenyl-1,4-dioxane-2,5-dione, a readily accessible chiral template. The present method involves two distinctive TiCl4/amine-mediated reactions: (i) an asymmetric Ti-crossed-Claisen Condensation of the chiral template with propanoyl chloride followed by methanolysis to afford methyl (2R)-(4E)-2-hydroxy-5-phenyl-2-propanoylpent-4-enoate, the key chiral synthon and (ii) a robust Ti-direct aldol addition reaction, instead of the reported lithium diisopropylamide/hexamethylphosphorictriamide (LDA/HMPA) or potassium hexamethyldisilazide (KHMDS)-mediated reaction, by using the trimethylsilyl (TMS) ether of α-acyl-γ-lactam to successfully furnish the new aldol adduct. Final oxidation, cyclization, and tert-butyldimethylsilyl (TBS) removal produced (–)-azaspirene from the key template in 23 steps (total yield 1.7 %).
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Asymmetric Ti-crossed Claisen Condensation: application to concise asymmetric total synthesis of alternaric acid.
Chemical communications (Cambridge England), 2013Co-Authors: Ryohei Nagase, Tomonori Misaki, Yumiko Oguni, Satoko Ureshino, Hiroaki Mura, Yoo TanabeAbstract:Asymmetric Ti-crossed Claisen Condensation utilizing the dioxane-2,5-dione chiral template and its successful application to total synthesis of chiral alternaric acid are described.
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reductive ti crossed Claisen Condensation between methyl α bromocarboxylates and acid chlorides utilizing a ticl4 pph3 n methylimidazole reagent
Chemistry Letters, 2007Co-Authors: Akira Iida, Tomonori Misaki, Syogo Nakazawa, Hidefumi Nakatsuji, Yoo TanabeAbstract:Reductive Ti-crossed Claisen Condensation between methyl α-bromocarboxylates and acid chlorides utilizing a TiCl4–PPh3–N-methylimidazole reagent proceeded smoothly to give the α-monosubstituted and...
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Powerful Ti-crossed Claisen Condensation between ketene silyl acetals or thioacetals and acid chlorides or acids.
Organic letters, 2006Co-Authors: Akira Iida, Tomohito Okabayashi, Tomonori Misaki, Syogo Nakazawa, Atsushi Horii, Yoo TanabeAbstract:A powerful Ti-crossed Claisen Condensation between ketene silyl acetals (KSAs) and acid chlorides was successfully performed to give α-monoalkylated esters and thermodynamically unfavorable (less accessible) α,α-dialkylated β-keto esters in good yield (46 examples; 41−98% yield). A closely related reaction between ketene silyl thioacetals (KSTAs) and acid chlorides also proceeded smoothly to give α-monoalkylated and α,α-dialkylated β-keto thioesters (21 examples; 61−97% yield). The present protocol was extended to the direct Condensation of KSAs with carboxylic acids (14 examples; 71−97% yield).
Yoshihiro Yoshida - One of the best experts on this subject based on the ideXlab platform.
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catalytic tmscl promoted powerful aldol addition and Claisen Condensation mediated by ticl4 bu3n agent comparison and evaluation with the mukaiyama aldol addition
Tetrahedron Letters, 1999Co-Authors: Yoshihiro Yoshida, Noriaki Matsumoto, Ryota Hamasaki, Yoo TanabeAbstract:Abstract MSCl catalyst (0.05 equiv) signifiantly promoted the TiCl 4 /Bu 3 N-mediated direct cross aldol additions of sterically crowded ketones and α-hetero substituted ketones, and also the direct Claisen Condensation between methyl esters.
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Catalytic TMSCl promoted powerful aldol addition and Claisen Condensation mediated by TiCl4/Bu3N agent: comparison and evaluation with the Mukaiyama aldol addition
Tetrahedron Letters, 1999Co-Authors: Yoshihiro Yoshida, Noriaki Matsumoto, Ryota Hamasaki, Yoo TanabeAbstract:Abstract MSCl catalyst (0.05 equiv) signifiantly promoted the TiCl 4 /Bu 3 N-mediated direct cross aldol additions of sterically crowded ketones and α-hetero substituted ketones, and also the direct Claisen Condensation between methyl esters.
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ticl4 bu3n catalytic tmsotf efficient agent for direct aldol addition and Claisen Condensation
Tetrahedron Letters, 1997Co-Authors: Yoshihiro Yoshida, Hiromasa Sumihara, R Hayashi, Yoo TanabeAbstract:Abstract TiCl 4 /Bu 3 N conducts highly efficient cross aldol additions between different ketones and between ketones and aldehydes, in good to excellent yields with high syn -stereoselectivities. As an extension, direct Claisen Condensation between methyl esters was also promoted by TiCl 4 /Bu 3 N with 0.05 equiv of TMSOTf co-catalyst.
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TiCl4/Bu3N/(catalytic TMSOTf): Efficient agent for direct aldol addition and Claisen Condensation
Tetrahedron Letters, 1997Co-Authors: Yoshihiro Yoshida, Hayashi R, Hiromasa Sumihara, Yoo TanabeAbstract:Abstract TiCl 4 /Bu 3 N conducts highly efficient cross aldol additions between different ketones and between ketones and aldehydes, in good to excellent yields with high syn -stereoselectivities. As an extension, direct Claisen Condensation between methyl esters was also promoted by TiCl 4 /Bu 3 N with 0.05 equiv of TMSOTf co-catalyst.
Hidefumi Nakatsuji - One of the best experts on this subject based on the ideXlab platform.
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Dehydration‐type Ti‐Claisen Condensation (Carbonhomologation) of α‐Heteroatom‐substituted Acetates with Alkyl Formates: Utilization as (Z)‐Stereodefined Cross‐coupling Partners and Application to Concise Synthesis of Strobilurin A
Advanced Synthesis & Catalysis, 2017Co-Authors: Hidefumi Nakatsuji, Risa Kamada, Hideya Kitaguchi, Yoo TanabeAbstract:Abstract. TiCl4–Et3N or –Bu3N reagent conducted a highly (Z)-stereoselective carbon homologation (dehydration type Ti-Claisen Condensation) of alkyl α-heteroatom (halo and sulfonyloxy)-substituted acetates (XCH2CO2R) with alkyl formates (HCO2R) to afford various alkyl β-alkoxy-α-halo or sulfonyloxy-substituted acrylates (24 examples; 51%–91% yield). Stereoretentive Suzuki-Miyaura, Negishi, and Sonogashira cross-couplings using the obtained methyl β-methoxy-α-halo or sulfonyloxy-substituted acrylates proceeded smoothly to produce a variety of β-alkoxy-α-substituted acrylates in moderate to high yield (35 examples; 29% – 99% yield). As a successful application, a 3-step straightforward synthesis of strobilurin A was performed utilizing the present reaction sequence (dehydration type Ti-Claisen Condensation and Suzuki-Miyaura cross-coupling), wherein the geometry of the three consecutive olefins (2E,3Z,5E) was completely maintained.
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Asymmetric Total Synthesis of (–)‐Azaspirene by Utilizing Ti‐Claisen Condensation and Ti‐Direct Aldol Reaction
European Journal of Organic Chemistry, 2016Co-Authors: Mikiko Sugi, Tomonori Misaki, Ryohei Nagase, Hidefumi Nakatsuji, Yoo TanabeAbstract:A successful asymmetric total synthesis of (–)-azaspirene has been accomplished by utilizing (3R)-6-cinnamyl-3-methyl-3-phenyl-1,4-dioxane-2,5-dione, a readily accessible chiral template. The present method involves two distinctive TiCl4/amine-mediated reactions: (i) an asymmetric Ti-crossed-Claisen Condensation of the chiral template with propanoyl chloride followed by methanolysis to afford methyl (2R)-(4E)-2-hydroxy-5-phenyl-2-propanoylpent-4-enoate, the key chiral synthon and (ii) a robust Ti-direct aldol addition reaction, instead of the reported lithium diisopropylamide/hexamethylphosphorictriamide (LDA/HMPA) or potassium hexamethyldisilazide (KHMDS)-mediated reaction, by using the trimethylsilyl (TMS) ether of α-acyl-γ-lactam to successfully furnish the new aldol adduct. Final oxidation, cyclization, and tert-butyldimethylsilyl (TBS) removal produced (–)-azaspirene from the key template in 23 steps (total yield 1.7 %).
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asymmetric total synthesis of azaspirene by utilizing ti Claisen Condensation and ti direct aldol reaction
European Journal of Organic Chemistry, 2016Co-Authors: Mikiko Sugi, Tomonori Misaki, Ryohei Nagase, Hidefumi Nakatsuji, Yoo TanabeAbstract:A successful asymmetric total synthesis of (–)-azaspirene has been accomplished by utilizing (3R)-6-cinnamyl-3-methyl-3-phenyl-1,4-dioxane-2,5-dione, a readily accessible chiral template. The present method involves two distinctive TiCl4/amine-mediated reactions: (i) an asymmetric Ti-crossed-Claisen Condensation of the chiral template with propanoyl chloride followed by methanolysis to afford methyl (2R)-(4E)-2-hydroxy-5-phenyl-2-propanoylpent-4-enoate, the key chiral synthon and (ii) a robust Ti-direct aldol addition reaction, instead of the reported lithium diisopropylamide/hexamethylphosphorictriamide (LDA/HMPA) or potassium hexamethyldisilazide (KHMDS)-mediated reaction, by using the trimethylsilyl (TMS) ether of α-acyl-γ-lactam to successfully furnish the new aldol adduct. Final oxidation, cyclization, and tert-butyldimethylsilyl (TBS) removal produced (–)-azaspirene from the key template in 23 steps (total yield 1.7 %).
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Practical and robust method for stereoselective preparations of ketene silyl (thio)acetal derivatives and NaOH-catalyzed crossed-Claisen Condensation between ketene silyl acetals and methyl esters
Tetrahedron, 2009Co-Authors: Kenta Takai, Akira Iida, Tomohito Okabayashi, Hidefumi Nakatsuji, Yuuya Nawate, Yoo TanabeAbstract:Abstract We developed an efficient, practical, and robust method for stereoselective preparations of (Z)-ketene trimethylsilyl (TMS) thioacetals from thioesters and alkyl (1Z)- or (1Z,3E)-1,3-bis(TMS)dienol ethers from alkyl β-ketoesters. The former preparation was performed by convenient procedure (LDA–TMSCl, 0–5 °C, 2.5 h), while the latter preparation involved convenient method A (2NaHMDS–2TMSCl) and cost-effective method B (NaH, NaHMDS–2TMSCl). The first catalytic NaOH-catalyzed crossed-Claisen Condensation between ketene silyl acetals and methyl esters proceeded successfully to give a variety of α-monomethyl β-ketoesters and inaccessible α,α-disubstituted β-ketoesters. For further extension, a couple of Claisen-aldol tandem reactions of the obtained β-ketoester analogues utilizing TiCl4 and TiCl4–Bu3N reagents smoothly proceeded with good to excellent stereoselectivity.
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reductive ti crossed Claisen Condensation between methyl α bromocarboxylates and acid chlorides utilizing a ticl4 pph3 n methylimidazole reagent
Chemistry Letters, 2007Co-Authors: Akira Iida, Tomonori Misaki, Syogo Nakazawa, Hidefumi Nakatsuji, Yoo TanabeAbstract:Reductive Ti-crossed Claisen Condensation between methyl α-bromocarboxylates and acid chlorides utilizing a TiCl4–PPh3–N-methylimidazole reagent proceeded smoothly to give the α-monosubstituted and...
Ryohei Nagase - One of the best experts on this subject based on the ideXlab platform.
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Asymmetric Total Synthesis of (–)‐Azaspirene by Utilizing Ti‐Claisen Condensation and Ti‐Direct Aldol Reaction
European Journal of Organic Chemistry, 2016Co-Authors: Mikiko Sugi, Tomonori Misaki, Ryohei Nagase, Hidefumi Nakatsuji, Yoo TanabeAbstract:A successful asymmetric total synthesis of (–)-azaspirene has been accomplished by utilizing (3R)-6-cinnamyl-3-methyl-3-phenyl-1,4-dioxane-2,5-dione, a readily accessible chiral template. The present method involves two distinctive TiCl4/amine-mediated reactions: (i) an asymmetric Ti-crossed-Claisen Condensation of the chiral template with propanoyl chloride followed by methanolysis to afford methyl (2R)-(4E)-2-hydroxy-5-phenyl-2-propanoylpent-4-enoate, the key chiral synthon and (ii) a robust Ti-direct aldol addition reaction, instead of the reported lithium diisopropylamide/hexamethylphosphorictriamide (LDA/HMPA) or potassium hexamethyldisilazide (KHMDS)-mediated reaction, by using the trimethylsilyl (TMS) ether of α-acyl-γ-lactam to successfully furnish the new aldol adduct. Final oxidation, cyclization, and tert-butyldimethylsilyl (TBS) removal produced (–)-azaspirene from the key template in 23 steps (total yield 1.7 %).
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asymmetric total synthesis of azaspirene by utilizing ti Claisen Condensation and ti direct aldol reaction
European Journal of Organic Chemistry, 2016Co-Authors: Mikiko Sugi, Tomonori Misaki, Ryohei Nagase, Hidefumi Nakatsuji, Yoo TanabeAbstract:A successful asymmetric total synthesis of (–)-azaspirene has been accomplished by utilizing (3R)-6-cinnamyl-3-methyl-3-phenyl-1,4-dioxane-2,5-dione, a readily accessible chiral template. The present method involves two distinctive TiCl4/amine-mediated reactions: (i) an asymmetric Ti-crossed-Claisen Condensation of the chiral template with propanoyl chloride followed by methanolysis to afford methyl (2R)-(4E)-2-hydroxy-5-phenyl-2-propanoylpent-4-enoate, the key chiral synthon and (ii) a robust Ti-direct aldol addition reaction, instead of the reported lithium diisopropylamide/hexamethylphosphorictriamide (LDA/HMPA) or potassium hexamethyldisilazide (KHMDS)-mediated reaction, by using the trimethylsilyl (TMS) ether of α-acyl-γ-lactam to successfully furnish the new aldol adduct. Final oxidation, cyclization, and tert-butyldimethylsilyl (TBS) removal produced (–)-azaspirene from the key template in 23 steps (total yield 1.7 %).
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Asymmetric Ti-crossed Claisen Condensation: application to concise asymmetric total synthesis of alternaric acid.
Chemical communications (Cambridge England), 2013Co-Authors: Ryohei Nagase, Tomonori Misaki, Yumiko Oguni, Satoko Ureshino, Hiroaki Mura, Yoo TanabeAbstract:Asymmetric Ti-crossed Claisen Condensation utilizing the dioxane-2,5-dione chiral template and its successful application to total synthesis of chiral alternaric acid are described.
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first sequential mukaiyama michael reaction crossed Claisen Condensation using two molar ketene silyl acetals and one molar α β unsaturated esters promoted by a naoh catalyst
ChemInform, 2010Co-Authors: Hiroaki Tamagaki, Ryohei Nagase, Yuuya Nawate, Yoo TanabeAbstract:A sequential Mukaiyama—Michael reaction and regioselective crossed-Claisen Condensation to afford 1,3,7-tricarbonyl scaffolds is developed using two equivalents of ketene silyl acetals (II)/(IV) and one equivalent α,β-unsaturated esters (I) in either a stepwise or one-pot procedure.
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First Sequential Mukaiyama—Michael Reaction/Crossed‐Claisen Condensation Using Two Molar Ketene Silyl Acetals and One Molar α,β‐Unsaturated Esters Promoted by a NaOH Catalyst.
ChemInform, 2010Co-Authors: Hiroaki Tamagaki, Ryohei Nagase, Yuuya Nawate, Yoo TanabeAbstract:A sequential Mukaiyama—Michael reaction and regioselective crossed-Claisen Condensation to afford 1,3,7-tricarbonyl scaffolds is developed using two equivalents of ketene silyl acetals (II)/(IV) and one equivalent α,β-unsaturated esters (I) in either a stepwise or one-pot procedure.