The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Masahiro Terada - One of the best experts on this subject based on the ideXlab platform.
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Bronsted Base catalyzed formal reductive 3 2 annulation of 4 4 4 trifluorocrotonate and α iminoketones
Chemistry: A European Journal, 2021Co-Authors: Azusa Kondoh, Masahiro TeradaAbstract:A formal reductive [3+2] annulation of 4,4,4-trifluorocrotonate and α-iminoketones was developed under Bronsted Base catalysis. A single phosphazene Base efficiently catalyzes the one-pot tandem reaction involving two mechanistically different elementary processes, namely the chemoselective reduction of an imine moiety of α-iminoketones with thiols as the reductant and the subsequent intermolecular Michael addition of an enolate of α-aminoketones concomitant with lactam formation. This operationally simple method provides β-trifluoromethyl-substituted γ-lactams with a tetrasubstituted carbon as a single diastereomer.
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synthesis of diarylalkanes through an intramolecular intermolecular addition sequence by auto tandem catalysis with strong Bronsted Base
Chemical Communications, 2020Co-Authors: Azusa Kondoh, Masahiro TeradaAbstract:An auto-tandem catalysis with a strong Bronsted Base enabled the synthesis of diarylalkanes containing a benzofuran moiety. Potassium tert-butoxide efficiently catalyzed both the intramolecular cyclization of less acidic ortho-alkynylaryl benzyl ethers and the following intermolecular addition of diarylmethanes to styrenes, demonstrating the high potential of the catalysis in organic synthesis.
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development of chiral ureates as chiral strong Bronsted Base catalysts
Journal of the American Chemical Society, 2020Co-Authors: Azusa Kondoh, Sho Ishikawa, Masahiro TeradaAbstract:Recently, chiral Bronsted Bases having high basicity have emerged as a powerful tool in developing new catalytic enantioselective reactions. However, such chiral strong Bronsted Base catalysts are still very scarce. Herein, we report the development of a chiral anionic Bronsted Base having a N,N'-dialkyl ureate moiety as a basic site. Its prominent catalytic activity was demonstrated in the enantioselective addition reactions of α-thioacetamides as less acidic pronucleophiles with various electrophiles. Thus, the newly developed chiral catalyst with high accessibility and structural tunability would expand the scope of viable enantioselective transformations under Bronsted Base catalysis.
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au catalyzed skeletal rearrangement of o propargylic oximes via n o bond cleavage with the aid of a Bronsted Base cocatalyst
Chemical Science, 2019Co-Authors: Keigo Shiga, Masahiro Terada, Ilya D Gridnev, Itaru NakamuraAbstract:O-Propargylic oximes that possess an electron-withdrawing aryl group on the oxime moiety undergo Au-catalyzed skeletal rearrangements via N–O bond cleavage to afford the corresponding 2H-1,3-oxazine derivatives. Our studies show that the inclusion of a Bronsted Base cocatalyst not only accelerates the reaction but also switches pathways of the skeletal rearrangement reaction, realizing divergent synthesis of heterocyclic compounds. Computational studies indicate that the elimination of propargylic proton in the cyclized vinylgold intermediate is rate-determining and both electron-withdrawing substituents at the oxime moiety and Base cocatalyst facilitate the proton elimination. Moreover, the protodeauration process proceeds stepwise involving N–O bond cleavage followed by recyclization to construct the oxazine core.
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efficient synthesis of polysubstituted pyrroles Based on 3 2 cycloaddition strategy utilizing 1 2 phospha brook rearrangement under Bronsted Base catalysis
Chemistry: A European Journal, 2018Co-Authors: Azusa Kondoh, Sho Ishikawa, Akio Iino, Takuma Aoki, Masahiro TeradaAbstract:An efficient method for the synthesis of polysubstituted pyrroles was established Based on the [3+2] cycloaddition strategy utilizing the [1,2]-phospha-Brook rearrangement under Bronsted Base catalysis. The less-explored approach of the [3+2] cycloaddition, that is, the reaction of a C3 subunit with imines, was successfully achieved by making use of newly designed C3 subunits containing the requisite umpolung. The two-step formal [3+2] cycloaddition involves the catalytic generation of an α-oxygenated propargyl anion through the [1,2]-phospha-Brook rearrangement followed by γ-addition to the imine under Bronsted Base catalysis and the subsequent intramolecular cyclization mediated by Au catalyst or a halogenation reagent to afford polysubstituted pyrroles having a variety of substituents in a positional selective manner. The pyrroles thus synthesized were amenable to further transformations, such as palladium-catalyzed cross-coupling reactions. The operationally very simple method with readily available substrates provides new access to a diverse array of well-organized polysubstituted pyrroles.
Masakatsu Shibasaki - One of the best experts on this subject based on the ideXlab platform.
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electrophilic activation of α β unsaturated amides catalytic asymmetric vinylogous conjugate addition of unsaturated γ butyrolactones
Chemistry: A European Journal, 2016Co-Authors: Ming Zhang, Naoya Kumagai, Masakatsu ShibasakiAbstract:Although catalytic asymmetric conjugate addition reactions have remarkably advanced over the last two decades, the application of less electrophilic α,β-unsaturated carboxylic acid derivatives in this useful reaction manifold remains challenging. Herein, we report that α,β-unsaturated 7-azaindoline amides act as reactive electrophiles to participate in catalytic diastereo- and enantioselective vinylogous conjugate addition of γ-butyrolactones in the presence of a cooperative catalyst comprising of a soft Lewis acid and a Bronsted Base. Reactions mostly reached completion with as little as 1 mol % of catalyst loading to give the desired conjugate adducts in a highly stereoselective manner.
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regiodivergent kinetic resolution of terminal and internal rac aziridines with malonates under dinuclear schiff Base catalysis
Journal of the American Chemical Society, 2014Co-Authors: Yingjie Xu, Keiichi Kaneko, Motomu Kanai, Masakatsu Shibasaki, Shigeki MatsunagaAbstract:Regiodivergent parallel kinetic resolution of aziridines with malonates was achieved under dinuclear Schiff Base catalysis. The regiodivergent reaction proceeded under catalyst-control irrespective of the substituents on the aziridines, and 2.5–10 mol % of a Y(OTf)3/La(OiPr)3/a dinucleating Schiff Base = 1:1:1 mixture gave versatile γ-amino acid derivatives in 96 → >99.5% ee. Not only terminal but also internal racemic aziridines reacted smoothly under suitably combined Lewis acid/Bronsted Base catalysis.
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cooperative activation of alkyne and thioamide functionalities direct catalytic asymmetric conjugate addition of terminal alkynes to α β unsaturated thioamides
Chemistry-an Asian Journal, 2011Co-Authors: Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:A detailed study of the direct catalytic asymmetric conjugate addition of terminal alkynes to α,β-unsaturated thioamides is described. A soft Lewis acid/hard Bronsted Base cooperative catalyst, comprising [Cu(CH(3)CN)(4)]PF(6), bisphosphine ligand, and Li(OC(6)H(4)-p-OMe) simultaneously activated both substrates to compensate for the low reactivity of copper alkynylide. A series of control experiments revealed that the intermediate copper-thioamide enolate functioned as a Bronsted Base to generate copper alkynylide from the terminal alkyne, thus driving the catalytic cycle through an efficient proton transfer between substrates. These findings led to the identification of a more convenient catalyst using potassium hexamethyldisilazane (KHMDS) as the Bronsted Base, which was particularly effective for the reaction of silylacetylenes. Divergent transformation of the thioamide functionality and a concise enantioselective synthesis of a GPR40 receptor agonist AMG-837 highlighted the synthetic utility of the present catalysis.
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enantioselective synthesis of a gpr40 agonist amg 837 via catalytic asymmetric conjugate addition of terminal alkyne to α β unsaturated thioamide
Organic Letters, 2011Co-Authors: Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:A concise enantioselective synthetic route to a potent GPR40 agonist AMG 837 is described. The crucial catalytic asymmetric conjugate addition of terminal alkyne was promoted by a soft Lewis acid/hard Bronsted Base cooperative catalyst, allowing efficient construction of the requisite stereogenic center. The thioamide functional group is key to both activation in asymmetric alkynylation and facile transformation into carboxylic acid.
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direct catalytic asymmetric aldol reaction of thioamides a concise asymmetric synthesis of r fluoxetine
Tetrahedron-asymmetry, 2010Co-Authors: Mitsutaka Iwata, Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:Abstract A direct catalytic asymmetric aldol reaction of aromatic aldehydes and thioamides is described. A soft Lewis acid/hard Bronsted Base cooperative catalyst comprising ( R , R )-Ph-BPE/[Cu(CH 3 CN) 4 ]PF 6 /Li(OC 6 H 4 - p -OMe) promoted the title reaction efficiently, triggered by in situ generation of the active thioamide enolate through a soft–soft interaction of Cu(I) and the thioamide. The aldol product was transformed into ( R )-fluoxetine, an antidepressant agent.
Azusa Kondoh - One of the best experts on this subject based on the ideXlab platform.
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Bronsted Base catalyzed formal reductive 3 2 annulation of 4 4 4 trifluorocrotonate and α iminoketones
Chemistry: A European Journal, 2021Co-Authors: Azusa Kondoh, Masahiro TeradaAbstract:A formal reductive [3+2] annulation of 4,4,4-trifluorocrotonate and α-iminoketones was developed under Bronsted Base catalysis. A single phosphazene Base efficiently catalyzes the one-pot tandem reaction involving two mechanistically different elementary processes, namely the chemoselective reduction of an imine moiety of α-iminoketones with thiols as the reductant and the subsequent intermolecular Michael addition of an enolate of α-aminoketones concomitant with lactam formation. This operationally simple method provides β-trifluoromethyl-substituted γ-lactams with a tetrasubstituted carbon as a single diastereomer.
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synthesis of diarylalkanes through an intramolecular intermolecular addition sequence by auto tandem catalysis with strong Bronsted Base
Chemical Communications, 2020Co-Authors: Azusa Kondoh, Masahiro TeradaAbstract:An auto-tandem catalysis with a strong Bronsted Base enabled the synthesis of diarylalkanes containing a benzofuran moiety. Potassium tert-butoxide efficiently catalyzed both the intramolecular cyclization of less acidic ortho-alkynylaryl benzyl ethers and the following intermolecular addition of diarylmethanes to styrenes, demonstrating the high potential of the catalysis in organic synthesis.
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development of chiral ureates as chiral strong Bronsted Base catalysts
Journal of the American Chemical Society, 2020Co-Authors: Azusa Kondoh, Sho Ishikawa, Masahiro TeradaAbstract:Recently, chiral Bronsted Bases having high basicity have emerged as a powerful tool in developing new catalytic enantioselective reactions. However, such chiral strong Bronsted Base catalysts are still very scarce. Herein, we report the development of a chiral anionic Bronsted Base having a N,N'-dialkyl ureate moiety as a basic site. Its prominent catalytic activity was demonstrated in the enantioselective addition reactions of α-thioacetamides as less acidic pronucleophiles with various electrophiles. Thus, the newly developed chiral catalyst with high accessibility and structural tunability would expand the scope of viable enantioselective transformations under Bronsted Base catalysis.
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efficient synthesis of polysubstituted pyrroles Based on 3 2 cycloaddition strategy utilizing 1 2 phospha brook rearrangement under Bronsted Base catalysis
Chemistry: A European Journal, 2018Co-Authors: Azusa Kondoh, Sho Ishikawa, Akio Iino, Takuma Aoki, Masahiro TeradaAbstract:An efficient method for the synthesis of polysubstituted pyrroles was established Based on the [3+2] cycloaddition strategy utilizing the [1,2]-phospha-Brook rearrangement under Bronsted Base catalysis. The less-explored approach of the [3+2] cycloaddition, that is, the reaction of a C3 subunit with imines, was successfully achieved by making use of newly designed C3 subunits containing the requisite umpolung. The two-step formal [3+2] cycloaddition involves the catalytic generation of an α-oxygenated propargyl anion through the [1,2]-phospha-Brook rearrangement followed by γ-addition to the imine under Bronsted Base catalysis and the subsequent intramolecular cyclization mediated by Au catalyst or a halogenation reagent to afford polysubstituted pyrroles having a variety of substituents in a positional selective manner. The pyrroles thus synthesized were amenable to further transformations, such as palladium-catalyzed cross-coupling reactions. The operationally very simple method with readily available substrates provides new access to a diverse array of well-organized polysubstituted pyrroles.
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Bronsted Base catalyzed reductive cyclization of alkynyl α iminoesters through auto tandem catalysis
Organic Letters, 2018Co-Authors: Azusa Kondoh, Masahiro TeradaAbstract:A novel reductive cyclization of alkynyl α-iminoesters was developed through auto-tandem catalysis with a Bronsted Base as the catalyst. The reaction system involves two mechanistically different elementary processes, both of which are efficiently catalyzed by an organosuperBase P2-tBu: the unprecedented reduction of α-iminoesters with 1-dodecanethiol as the reductant to provide α-aminoesters and the following intramolecular addition of ester enolates to an alkyne. The operationally simple reaction under mild conditions provides new efficient access to N-H indoline derivatives, demonstrating the high potential of auto-tandem catalysis with a Bronsted Base as a methodology for organic synthesis.
Ryo Yazaki - One of the best experts on this subject based on the ideXlab platform.
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cooperative activation of alkyne and thioamide functionalities direct catalytic asymmetric conjugate addition of terminal alkynes to α β unsaturated thioamides
Chemistry-an Asian Journal, 2011Co-Authors: Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:A detailed study of the direct catalytic asymmetric conjugate addition of terminal alkynes to α,β-unsaturated thioamides is described. A soft Lewis acid/hard Bronsted Base cooperative catalyst, comprising [Cu(CH(3)CN)(4)]PF(6), bisphosphine ligand, and Li(OC(6)H(4)-p-OMe) simultaneously activated both substrates to compensate for the low reactivity of copper alkynylide. A series of control experiments revealed that the intermediate copper-thioamide enolate functioned as a Bronsted Base to generate copper alkynylide from the terminal alkyne, thus driving the catalytic cycle through an efficient proton transfer between substrates. These findings led to the identification of a more convenient catalyst using potassium hexamethyldisilazane (KHMDS) as the Bronsted Base, which was particularly effective for the reaction of silylacetylenes. Divergent transformation of the thioamide functionality and a concise enantioselective synthesis of a GPR40 receptor agonist AMG-837 highlighted the synthetic utility of the present catalysis.
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enantioselective synthesis of a gpr40 agonist amg 837 via catalytic asymmetric conjugate addition of terminal alkyne to α β unsaturated thioamide
Organic Letters, 2011Co-Authors: Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:A concise enantioselective synthetic route to a potent GPR40 agonist AMG 837 is described. The crucial catalytic asymmetric conjugate addition of terminal alkyne was promoted by a soft Lewis acid/hard Bronsted Base cooperative catalyst, allowing efficient construction of the requisite stereogenic center. The thioamide functional group is key to both activation in asymmetric alkynylation and facile transformation into carboxylic acid.
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direct catalytic asymmetric aldol reaction of thioamides a concise asymmetric synthesis of r fluoxetine
Tetrahedron-asymmetry, 2010Co-Authors: Mitsutaka Iwata, Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:Abstract A direct catalytic asymmetric aldol reaction of aromatic aldehydes and thioamides is described. A soft Lewis acid/hard Bronsted Base cooperative catalyst comprising ( R , R )-Ph-BPE/[Cu(CH 3 CN) 4 ]PF 6 /Li(OC 6 H 4 - p -OMe) promoted the title reaction efficiently, triggered by in situ generation of the active thioamide enolate through a soft–soft interaction of Cu(I) and the thioamide. The aldol product was transformed into ( R )-fluoxetine, an antidepressant agent.
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direct catalytic asymmetric addition of allyl cyanide to ketones via soft lewis acid hard Bronsted Base hard lewis Base catalysis
Journal of the American Chemical Society, 2010Co-Authors: Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:We report that a hard Lewis Base substantially affects the reaction efficiency of direct catalytic asymmetric γ-addition of allyl cyanide (1a) to ketones promoted by a soft Lewis acid/hard Bronsted Base catalyst. Mechanistic studies have revealed that Cu/(R,R)-Ph-BPE and Li(OC6H4-p-OMe) serve as a soft Lewis acid and a hard Bronsted Base, respectively, allowing for deprotonative activation of 1a as the rate-determining step. A ternary catalytic system comprising a soft Lewis acid/hard Bronsted Base and an additional hard Lewis Base, in which the basicity of the hard Bronsted Base Li(OC6H4-p-OMe) was enhanced by phosphine oxide (the hard Lewis Base) through a hard−hard interaction, outperformed the previously developed binary soft Lewis acid/hard Bronsted Base catalytic system, leading to higher yields and enantioselectivities while using one-tenth the catalyst loading and one-fifth the amount of 1a. This second-generation catalyst allows efficient access to highly enantioenriched tertiary alcohols under n...
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direct catalytic asymmetric addition of allyl cyanide to ketones via soft lewis acid hard Bronsted Base hard lewis Base catalysis
Journal of the American Chemical Society, 2010Co-Authors: Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:We report that a hard Lewis Base substantially affects the reaction efficiency of direct catalytic asymmetric gamma-addition of allyl cyanide (1a) to ketones promoted by a soft Lewis acid/hard Bronsted Base catalyst. Mechanistic studies have revealed that Cu/(R,R)-Ph-BPE and Li(OC(6)H(4)-p-OMe) serve as a soft Lewis acid and a hard Bronsted Base, respectively, allowing for deprotonative activation of 1a as the rate-determining step. A ternary catalytic system comprising a soft Lewis acid/hard Bronsted Base and an additional hard Lewis Base, in which the basicity of the hard Bronsted Base Li(OC(6)H(4)-p-OMe) was enhanced by phosphine oxide (the hard Lewis Base) through a hard-hard interaction, outperformed the previously developed binary soft Lewis acid/hard Bronsted Base catalytic system, leading to higher yields and enantioselectivities while using one-tenth the catalyst loading and one-fifth the amount of 1a. This second-generation catalyst allows efficient access to highly enantioenriched tertiary alcohols under nearly ideal atom-economical conditions (0.5-1 mol % catalyst loading and a substrate molar ratio of 1:2).
Naoya Kumagai - One of the best experts on this subject based on the ideXlab platform.
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electrophilic activation of α β unsaturated amides catalytic asymmetric vinylogous conjugate addition of unsaturated γ butyrolactones
Chemistry: A European Journal, 2016Co-Authors: Ming Zhang, Naoya Kumagai, Masakatsu ShibasakiAbstract:Although catalytic asymmetric conjugate addition reactions have remarkably advanced over the last two decades, the application of less electrophilic α,β-unsaturated carboxylic acid derivatives in this useful reaction manifold remains challenging. Herein, we report that α,β-unsaturated 7-azaindoline amides act as reactive electrophiles to participate in catalytic diastereo- and enantioselective vinylogous conjugate addition of γ-butyrolactones in the presence of a cooperative catalyst comprising of a soft Lewis acid and a Bronsted Base. Reactions mostly reached completion with as little as 1 mol % of catalyst loading to give the desired conjugate adducts in a highly stereoselective manner.
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cooperative activation of alkyne and thioamide functionalities direct catalytic asymmetric conjugate addition of terminal alkynes to α β unsaturated thioamides
Chemistry-an Asian Journal, 2011Co-Authors: Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:A detailed study of the direct catalytic asymmetric conjugate addition of terminal alkynes to α,β-unsaturated thioamides is described. A soft Lewis acid/hard Bronsted Base cooperative catalyst, comprising [Cu(CH(3)CN)(4)]PF(6), bisphosphine ligand, and Li(OC(6)H(4)-p-OMe) simultaneously activated both substrates to compensate for the low reactivity of copper alkynylide. A series of control experiments revealed that the intermediate copper-thioamide enolate functioned as a Bronsted Base to generate copper alkynylide from the terminal alkyne, thus driving the catalytic cycle through an efficient proton transfer between substrates. These findings led to the identification of a more convenient catalyst using potassium hexamethyldisilazane (KHMDS) as the Bronsted Base, which was particularly effective for the reaction of silylacetylenes. Divergent transformation of the thioamide functionality and a concise enantioselective synthesis of a GPR40 receptor agonist AMG-837 highlighted the synthetic utility of the present catalysis.
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enantioselective synthesis of a gpr40 agonist amg 837 via catalytic asymmetric conjugate addition of terminal alkyne to α β unsaturated thioamide
Organic Letters, 2011Co-Authors: Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:A concise enantioselective synthetic route to a potent GPR40 agonist AMG 837 is described. The crucial catalytic asymmetric conjugate addition of terminal alkyne was promoted by a soft Lewis acid/hard Bronsted Base cooperative catalyst, allowing efficient construction of the requisite stereogenic center. The thioamide functional group is key to both activation in asymmetric alkynylation and facile transformation into carboxylic acid.
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direct catalytic asymmetric aldol reaction of thioamides a concise asymmetric synthesis of r fluoxetine
Tetrahedron-asymmetry, 2010Co-Authors: Mitsutaka Iwata, Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:Abstract A direct catalytic asymmetric aldol reaction of aromatic aldehydes and thioamides is described. A soft Lewis acid/hard Bronsted Base cooperative catalyst comprising ( R , R )-Ph-BPE/[Cu(CH 3 CN) 4 ]PF 6 /Li(OC 6 H 4 - p -OMe) promoted the title reaction efficiently, triggered by in situ generation of the active thioamide enolate through a soft–soft interaction of Cu(I) and the thioamide. The aldol product was transformed into ( R )-fluoxetine, an antidepressant agent.
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direct catalytic asymmetric addition of allyl cyanide to ketones via soft lewis acid hard Bronsted Base hard lewis Base catalysis
Journal of the American Chemical Society, 2010Co-Authors: Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:We report that a hard Lewis Base substantially affects the reaction efficiency of direct catalytic asymmetric γ-addition of allyl cyanide (1a) to ketones promoted by a soft Lewis acid/hard Bronsted Base catalyst. Mechanistic studies have revealed that Cu/(R,R)-Ph-BPE and Li(OC6H4-p-OMe) serve as a soft Lewis acid and a hard Bronsted Base, respectively, allowing for deprotonative activation of 1a as the rate-determining step. A ternary catalytic system comprising a soft Lewis acid/hard Bronsted Base and an additional hard Lewis Base, in which the basicity of the hard Bronsted Base Li(OC6H4-p-OMe) was enhanced by phosphine oxide (the hard Lewis Base) through a hard−hard interaction, outperformed the previously developed binary soft Lewis acid/hard Bronsted Base catalytic system, leading to higher yields and enantioselectivities while using one-tenth the catalyst loading and one-fifth the amount of 1a. This second-generation catalyst allows efficient access to highly enantioenriched tertiary alcohols under n...
