The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Eiichi Nakamura - One of the best experts on this subject based on the ideXlab platform.
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Selectivities in carbometalation of olefins. Experimental and theoretical studies
2015Co-Authors: Eiichi NakamuraAbstract:Despite the potential synthetic utility of the reaction, the elements that control the regio- and stereochemistry of t he addition of a n organometallic reagent to an olefin have not received careful attention. Our recent studies on the selectivities in organometallic addition to Cyclopropenone acetals have revealed some principles of regio- and stereocontrol in organometallic additions to olefins. As guided by the computational analysis of the experimental selectivities, it was found that the controlling elements are quite different from those known for organometallic additions to carbonyl compounds
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thermal and palladium catalyzed 3 2 synthesis of cyclopentadienone acetals from Cyclopropenone acetals and acetylenes
Organic Letters, 2004Co-Authors: Hiroyuki Isobe, Hidetoshi Tokuyama, Sota Sato, Takatsugu Tanaka, Eiichi NakamuraAbstract:Substituted cyclopentadienone acetals (CPDAs) were synthesized by a thermal or palladium-catalyzed [3 + 2] cycloaddition reaction of a substituted Cyclopropenone acetal to an electron-deficient acetylene. The synthesis afforded di-, tri-, and tetrasubstituted CPDAs of considerable structural varieties that undergo Diels−Alder reaction to produce bicyclo[2.2.1]heptenes.
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Cyclopropenone 1 3 propanediyl acetal
e-EROS Encyclopedia of Reagents for Organic Synthesis, 2001Co-Authors: Shigeru Yamago, Eiichi NakamuraAbstract:[60935-21-9] C6H8O2 (MW 112.12) InChI = 1S/C6H8O2/c1-4-7-6(2-3-6)8-5-1/h2-3H,1,4-5H2 InChIKey = HIQNFQSASCLYLW-UHFFFAOYSA-N (Cyclopropenone synthesis;4 vinylcarbene formation;1 acceptor of organometallic reagents;13 dienophile15) Physical Data: bp 30–35 °C/1.25 mmHg. Solubility: insol H2O. Form Supplied in: colorless liquid. Analysis of Reagent Purity: GLC, NMR. Preparative Method: the best current preparation of Cyclopropenone acetals involves the reaction of 1,3-dichloroacetone 1,3-propanediyl acetal with Sodium Amide in a liq. NH3/Et2O mixture.2 The latter acetal can be prepared in high yield from commercially available 1,3-dichloroacetone and 1,3-propanediol. This method is superior to the previous method which employs the less convenient reagents KNH2 and 1-chloro-3-bromoacetone 1,3-propanediyl acetal.3 Purification: distillation under reduced pressure. Handling, Storage, and Precautions: Cyclopropenone acetals may be stored in a refrigerator.
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macrocarbocycle synthesis by copper and silver mediated cyclization of tethered Cyclopropenone acetals electronic tuning of metal vinylcarbene complex into vinylmetallic species
Organic Letters, 1999Co-Authors: And Masahiro Yamanaka, Eiichi NakamuraAbstract:Synthesis of n-membered medium and macrocarbocycles through intramolecular sp2−sp2 C−C bond formation was achieved with the aid of CuOTf or AgOTf by intramolecular coupling reaction of Cyclopropenone acetals tethered by a methylene chain of (n − 4) carbon atoms. The reaction has proved to be useful for the synthesis of large carbocycles (n > 13) in yields as high as 78%, and most notably also for an eight-membered carbocycle in 88% yield.
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synthesis of Cyclopropenone containing amino acid mimic addition of cyclopropenyl cerium reagent to α amino aldehydes
ChemInform, 1995Co-Authors: Hidetoshi Tokuyama, Masahiko Isaka, Eiichi NakamuraAbstract:Abstract A novel amino acid mimic, 2-(2-amino-1-hydroxyalkyl)-Cyclopropenone, has been prepared via chelation controlled addition of a cyclopropenyl cerium reagent to an α-amino aldehyde.
Dale L Boger - One of the best experts on this subject based on the ideXlab platform.
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intramolecular 1 2 and 3 2 cycloaddition reactions of Cyclopropenone ketals
ChemInform, 2010Co-Authors: Paresma R Patel, Dale L BogerAbstract:The first intramolecular thermal reactions of Cyclopropenone ketals are reported and the work examined substrates tethered to an electron-deficient olefin bearing a single electron-withdrawing substituent. Whereas the intermolecular variants of the reactions provide only the products of an endo-selective [1 + 2] cycloaddition or a carbonyl addition reaction of a thermally generated π-delocalized singlet vinylcarbene, the intramolecular variants provide either [1 + 2] or [3 + 2] cycloadducts in reactions that depend on the reaction conditions, the alkene-activating substituent, and the nature of the tethering. In addition to providing key mechanistic insights into the thermal [3 + 2] cycloaddition reaction for such substrates, they were also found to proceed under conditions that reflect the ease and regioselectivity of the Cyclopropenone ketal cleavage for π-delocalized singlet vinylcarbene generation. The most effective combination of structural features that impact the reactivity was observed with subst...
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intramolecular diels alder reactions of Cyclopropenone ketals
Organic Letters, 2010Co-Authors: Paresma R Patel, Dale L BogerAbstract:The first intramolecular cycloaddition reactions of Cyclopropenone ketals with tethered electron-deficient, electron-rich, and neutral 1-substituted dienes are reported, constituting inverse electron demand, normal, and neutral Diels-Alder reactions, that provide exclusively the exo [4 + 2] cycloaddition products without the intervention of [1 + 2], [3 + 2], or [3 + 4] cycloadducts in reactions whose courses do not depend on the reaction conditions, the diene activating substituent, or the nature of the tethering.
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preparation and three carbon two carbon cycloaddition of Cyclopropenone 1 3 propanediol ketal 5 5 dicyano 4 phenyl 2 cyclopenten 1 one 1 3 propanediol ketal
Organic Syntheses, 2003Co-Authors: Dale L Boger, Christine E Brotherton, Gunda I GeorgAbstract:Preparation and three-carbon + two-carbon cycloaddition of Cyclopropenone 1,3-propanediol ketal: 5,5-Dicyano-4-phenyl-2-cyclopenten-1-one 1,3-propanediol ketal intermediate: 2-(bromomethyl)-2-(chloromethyl)-1,3-dioxane intermediate: Cyclopropenone 1,3-propanediol ketal product: 5,5-dicyano-4-phenyl-2-cyclopenten-1-one 1,3-propanediol ketal Keywords: acetal (and thioacetal) formation; alkylation, C-alkylation; annulation, carbocyclic-[3]; annulation, carbocyclic-[5]; cyclization, condensation; cyclization, cycloaddition; halogenation, bromination; halogenation, bromination; ring expansion reactions; potassium amide, preparation of; pressure reactions, use of resealable glass tubes
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diels alder reactions of Cyclopropenone ketals a concise tropolone annulation applicable to rubrolone c ring introduction
Journal of Organic Chemistry, 1994Co-Authors: Dale L Boger, Yan ZhuAbstract:A concise tropolone annulation applicable to rubrolone C ring introduc- tion is detailed based on the room-temperature [4+2] cycloaddition rea- ction of the Cyclopropenone ketal (10) with the oxygenated diene (9). Conversion of the sensitive [4+2] cycloadduct (11) to the norcaradiene (18), low temperature electrocyclic rearrangement to a cycloheptatrie- none ketal, and tautomerization to (12) provided a fully oxygenated tropolone analogous to that found in rubrolone
Gunda I Georg - One of the best experts on this subject based on the ideXlab platform.
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preparation and three carbon two carbon cycloaddition of Cyclopropenone 1 3 propanediol ketal 5 5 dicyano 4 phenyl 2 cyclopenten 1 one 1 3 propanediol ketal
Organic Syntheses, 2003Co-Authors: Dale L Boger, Christine E Brotherton, Gunda I GeorgAbstract:Preparation and three-carbon + two-carbon cycloaddition of Cyclopropenone 1,3-propanediol ketal: 5,5-Dicyano-4-phenyl-2-cyclopenten-1-one 1,3-propanediol ketal intermediate: 2-(bromomethyl)-2-(chloromethyl)-1,3-dioxane intermediate: Cyclopropenone 1,3-propanediol ketal product: 5,5-dicyano-4-phenyl-2-cyclopenten-1-one 1,3-propanediol ketal Keywords: acetal (and thioacetal) formation; alkylation, C-alkylation; annulation, carbocyclic-[3]; annulation, carbocyclic-[5]; cyclization, condensation; cyclization, cycloaddition; halogenation, bromination; halogenation, bromination; ring expansion reactions; potassium amide, preparation of; pressure reactions, use of resealable glass tubes
Hidetoshi Tokuyama - One of the best experts on this subject based on the ideXlab platform.
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thermal and palladium catalyzed 3 2 synthesis of cyclopentadienone acetals from Cyclopropenone acetals and acetylenes
Organic Letters, 2004Co-Authors: Hiroyuki Isobe, Hidetoshi Tokuyama, Sota Sato, Takatsugu Tanaka, Eiichi NakamuraAbstract:Substituted cyclopentadienone acetals (CPDAs) were synthesized by a thermal or palladium-catalyzed [3 + 2] cycloaddition reaction of a substituted Cyclopropenone acetal to an electron-deficient acetylene. The synthesis afforded di-, tri-, and tetrasubstituted CPDAs of considerable structural varieties that undergo Diels−Alder reaction to produce bicyclo[2.2.1]heptenes.
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Cyclopropenone containing cysteine proteinase inhibitors synthesis and enzyme inhibitory activities
Bioorganic & Medicinal Chemistry, 1999Co-Authors: Ryoichi Ando, Toshiro Sakaki, Yasuhiro Morinaka, Chizuko Takahashi, Yoshikuni Tamao, Narihiko Yoshii, Sota Katayama, Kenichi Saito, Hidetoshi Tokuyama, Masahiko IsakaAbstract:Abstract By focusing on the amphiphilic properties of Cyclopropenone (e.g. a good electrophile and a precursor for a stable 2π-aromatic hydroxycyclopropenium cation), a new class of cysteine proteinase inhibitors containing a Cyclopropenone moiety was designed. For the purpose of the present research, we needed to devise a new method to introduce a peptide-related moiety as a substituent on the Cyclopropenone residue. We investigated the reaction of metalated Cyclopropenone acetal derivatives ( 2 , R 2 =metal) with N -protected α-aminoaldehydes 4 to obtain the adduct 5 , and succeeded in the preparation of highly potentiated cysteine proteinase inhibitors 8 after several steps transformations. They showed strong inhibitory activities only to cysteine proteinases such as calpain, papain, cathepsin B, and cathepsin L and not to serine (e.g. thrombin and cathepsin G) and asparatic protainases (e.g. cathepsin D). Kinetic studies indicated that they are competitive inhibitors, and by the examinations of their inhibitory mechanism it became clear that they are reversible inhibitors. ©
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synthesis of Cyclopropenone containing amino acid mimic addition of cyclopropenyl cerium reagent to α amino aldehydes
ChemInform, 1995Co-Authors: Hidetoshi Tokuyama, Masahiko Isaka, Eiichi NakamuraAbstract:Abstract A novel amino acid mimic, 2-(2-amino-1-hydroxyalkyl)-Cyclopropenone, has been prepared via chelation controlled addition of a cyclopropenyl cerium reagent to an α-amino aldehyde.
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synthesis and biological activities of Cyclopropenone antibiotic penitricin and congeners
The Journal of Antibiotics, 1992Co-Authors: Hidetoshi Tokuyama, Eiichi Nakamura, Ryoichi Ando, Masahiko Isaka, Yasuhiro MorinakaAbstract:A number of derivatives of the Cyclopropenone antibiotic penitricin have been synthesized by the reaction of metalated Cyclopropenone acetals with electrophiles. Studies on the antimicrobial structure-activity relationships indicated that the penitricin skeleton, hydroxymethylCyclopropenone, is indispensable for antimicrobial activity. These compounds were also found to display cytotoxic activity.
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thermal reactions of substituted Cyclopropenone acetals regio and stereochemistry of vinylcarbene formation and low temperature 3 2 cycloaddition
Journal of the American Chemical Society, 1992Co-Authors: Hidetoshi Tokuyama, Masahiko Isaka, Eiichi NakamuraAbstract:Cyclopropenone acetals bearing olefinic substituents of diverse electronic character have been synthesized and examined for their thermal behavior toward water and electron-deficient olefins. The substituted cyclopropenes underwent regio- and stereoselective hydration to give acrylate derivatives via vinylcarbene species, providing new data on the regio- and stereochemistry of vinylcarbene species. The also underwent regioselective [3+2] cycloadditions to electron-deficient olefins to fibe a viariety of cyclopentenone acetals
Masahiko Isaka - One of the best experts on this subject based on the ideXlab platform.
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Cyclopropenone containing cysteine proteinase inhibitors synthesis and enzyme inhibitory activities
Bioorganic & Medicinal Chemistry, 1999Co-Authors: Ryoichi Ando, Toshiro Sakaki, Yasuhiro Morinaka, Chizuko Takahashi, Yoshikuni Tamao, Narihiko Yoshii, Sota Katayama, Kenichi Saito, Hidetoshi Tokuyama, Masahiko IsakaAbstract:Abstract By focusing on the amphiphilic properties of Cyclopropenone (e.g. a good electrophile and a precursor for a stable 2π-aromatic hydroxycyclopropenium cation), a new class of cysteine proteinase inhibitors containing a Cyclopropenone moiety was designed. For the purpose of the present research, we needed to devise a new method to introduce a peptide-related moiety as a substituent on the Cyclopropenone residue. We investigated the reaction of metalated Cyclopropenone acetal derivatives ( 2 , R 2 =metal) with N -protected α-aminoaldehydes 4 to obtain the adduct 5 , and succeeded in the preparation of highly potentiated cysteine proteinase inhibitors 8 after several steps transformations. They showed strong inhibitory activities only to cysteine proteinases such as calpain, papain, cathepsin B, and cathepsin L and not to serine (e.g. thrombin and cathepsin G) and asparatic protainases (e.g. cathepsin D). Kinetic studies indicated that they are competitive inhibitors, and by the examinations of their inhibitory mechanism it became clear that they are reversible inhibitors. ©
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synthesis of Cyclopropenone containing amino acid mimic addition of cyclopropenyl cerium reagent to α amino aldehydes
ChemInform, 1995Co-Authors: Hidetoshi Tokuyama, Masahiko Isaka, Eiichi NakamuraAbstract:Abstract A novel amino acid mimic, 2-(2-amino-1-hydroxyalkyl)-Cyclopropenone, has been prepared via chelation controlled addition of a cyclopropenyl cerium reagent to an α-amino aldehyde.
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synthesis and biological activities of Cyclopropenone antibiotic penitricin and congeners
The Journal of Antibiotics, 1992Co-Authors: Hidetoshi Tokuyama, Eiichi Nakamura, Ryoichi Ando, Masahiko Isaka, Yasuhiro MorinakaAbstract:A number of derivatives of the Cyclopropenone antibiotic penitricin have been synthesized by the reaction of metalated Cyclopropenone acetals with electrophiles. Studies on the antimicrobial structure-activity relationships indicated that the penitricin skeleton, hydroxymethylCyclopropenone, is indispensable for antimicrobial activity. These compounds were also found to display cytotoxic activity.
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thermal reactions of substituted Cyclopropenone acetals regio and stereochemistry of vinylcarbene formation and low temperature 3 2 cycloaddition
Journal of the American Chemical Society, 1992Co-Authors: Hidetoshi Tokuyama, Masahiko Isaka, Eiichi NakamuraAbstract:Cyclopropenone acetals bearing olefinic substituents of diverse electronic character have been synthesized and examined for their thermal behavior toward water and electron-deficient olefins. The substituted cyclopropenes underwent regio- and stereoselective hydration to give acrylate derivatives via vinylcarbene species, providing new data on the regio- and stereochemistry of vinylcarbene species. The also underwent regioselective [3+2] cycloadditions to electron-deficient olefins to fibe a viariety of cyclopentenone acetals
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one pot synthesis of substituted Cyclopropenone ketals via alkylation of 3 3 dialkoxy 2 sodiocyclopropenes
Tetrahedron Letters, 1991Co-Authors: Masahiko Isaka, Yasuhiro Morinaka, Ryoichi Ando, Eiichi NakamuraAbstract:Abstract A variety of substituted Cyclopropenone ketals have been prepared by electrophilic trapping (protonolysis and alkylation) of sodium salts of Cyclopropenone ketals that have been generated directly from the ketals of 1,3-dichloroacetone derivatives through cyclization with NaNH 2 in a liq. NH 3 /ether mixture.
