- Diastereoselective photocycloaddition reactions of 2-naphthalenecarboxylates and 2,3-naphthalenedicarboxylates with furans governed by chiral auxiliaries and hydrogen bonding interactions
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By using chiral auxiliaries and hydrogen bonding interactions, we have developed diastereoselective photocycloaddition of 2-naphthalenecarboxylates and 2,3-naphthalenedicarboxylates with furan derivatives. In photoreactions of (?)-menthyl 2-naphthalenecarboxylate with furan and 3-furanmethanol, respective maximum 48% and 40% diastereomeric excesses (d.e.) are observed. In photoreactions of di-8-phenyl-(?)-menthyl 2,3-naphthalenedicarboxylate with 3-furanmethanol, maximum 67% d.e. is obtained. Use of solvents of low polarity, low temperatures and low furan concentration leads to increased diastereoselectivities. Variable-temperature (VT) NMR and fluorescence quenching studies indicate that hydrogen bonding interactions between the carbonyl oxygen of naphthalenecarboxylic acid esters and the OH group in 3-furanmethanol take place in both the ground and excited states. The results of computational studies show that geometries of C2 symmetric naphthalenedicarboxylate reactants are important in governing the high diastereoselectivity in the photoreactions of 2,3-naphthalenedicarboxylates.
- Maeda, Hajime,Koshio, Norihiro,Tachibana, Yuko,Chiyonobu, Kazuhiko,Konishi, Gen-ichi,Mizuno, Kazuhiko
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- Synthesis of the Privileged 8-Arylmenthol Class by Radical Arylation of Isopulegol
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Hydrogen atom transfer (HAT) circumvents a disfavored Friedel-Crafts reaction in the derivatization of the inexpensive monoterpene isopulegol. A variety of readily prepared aryl and heteroaryl sulfonates undergo a formal hydroarylation to form 8-arylmenthols, privileged scaffolds for asymmetric synthesis, as typified by 8-phenylmenthol. High stereoselectivity is observed in related systems. This use of HAT significantly extends the chiral pool from the inexpensive monoterpene isopulegol.
- Crossley, Steven W. M.,Martinez, Ruben M.,Guevara-Zuluaga, Sebastián,Shenvi, Ryan A.
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p. 2620 - 2623
(2016/06/15)
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- Asymmetric Synthesis of 2-Alkyl(Aryl)-2,3-dihydro-4-pyridones by Addition of Grignard Reagents to Chiral 1-Acyl-4-methoxypyridinium Salts
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Grignard addition to a chiral 1-acyl-4-methoxypyridinium salt provides synthetically useful 2-alkyl(aryl)-2,3-dihydro-4-pyridones in high diastereomeric excess.
- Comins, Daniel L.,Goehring, R. Richard,Joseph, Sajan P.,O'Connor, Sean
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p. 2574 - 2576
(2007/10/02)
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- Asymmetric Two-Fold Michael Reaction. Synthesis of Optically Active 4-Substituted 1-Decalones from Trimethylsilyl Enol Ether of 1-Acetylcyclohexene
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Acrylates having a chiral auxiliary react with the trimethylsilyl enol ether of 1-acetylcyclohexene in the presence of Et2AlCl to give 4-substituted 1-decalones with 0-70percent diastereoselectivity.The absolute stereostructure of the decalones have been determined by applying the exciton chirality method to the dibenzoate derivative.
- Hagiwara, Hisahiro,Akama, Tsutomu,Okano, Akihiro,Uda, Hisashi
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p. 2149 - 2152
(2007/10/02)
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- SYNTHESIS OF OPTICALLY ACTIVE 3-OXA-CARBACYCLIN PRECURSORS FEATURING ASYMMETRIC HORNER-EMMONS REACTION
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An enantiselective synthesis of 5 is described.Asymmetric Horner-Emmons reactions with the chiral phosphonate 6 are key steps in the synthesis of the allylic alcohols E-8 and E-11 from the ketones 5 and 9, respectively.
- Gais, Hans-Joachim,Schmiedl, Gerhard,Ball, Walter A.,Bund, Joerg,Hellmann, Gunther,Erdelmeier, Irene
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p. 1773 - 1774
(2007/10/02)
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- Large-Scale Preparation of Pure (+)-(1S,2R,5S)-5-Methyl-2-(1-methyl-1-phenylethyl)cyclohexanol
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A procedure is described for the preparation of (S)-(-)pulegone, (-)-1, starting from (S)-(-)citronellol, (-)-6, in a preparative scale.Compound (-)-1 can easily be converted into (+)-(1S,2R,5S)-5-methyl-2-(1-methyl-1-phenylethyl)cyclohexanol: (+)-2 by a procedure described in literature, which was simplified essentially.Now (+)-2 is accessible in larger amounts and thus is available as an efficient chiral auxiliary in stoichiometric asymmetric syntheses.
- Buschmann, Helmut,Scharf, Hans-Dieter
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p. 827 - 830
(2007/10/02)
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