- 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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- Synthesis and characterization of all stereoisomers of 8-phenylmenthol
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New, improved and/or specific syntheses of the diastereoisomers of (-)-8-phenylmenthol are described. The configurations of these products, usable as chiral auxiliaries, were confirmed by X-ray diffractometry of their 3,5-dinitrobenzoates.
- Fernandez, Franco,Garcia-Mera, Xerardo,Lopez, Carmen,Rodriguez, Gonzalo,Rodriguez-Borges, Jose Enrique
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p. 4805 - 4815
(2007/10/03)
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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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- PREPARATION OF THREE DIASTEREOISOMERS OF 2-(1-METHYL-1-PHENYLETHYL)-5-METHYLCYCLOHEXAN-1-OL FROM (R)-(+)-PULEGONE
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New isolation of (1R,2S,5R)-(-)-2-(1-methyl-1-phenylethyl)-5-methylcyclohexan-1-ol ((-)-8-phenylmenthol, Ia), prepared from (R)-(+)-pulegone, is described.The method consists in the preparation of phenylcarbamate of Ia and its transesterification with ethanol.Further two diastereoisomers of (-)-8-phenylmenthol were isolated: the (1S,2R,5R)-isomer IIa and the (1R,2R,5R)-isomer IIIa.Compounds Ia, IIa and IIIa were converted into their respective glyoxylates Ic, IIc and IIIc.
- Cervinka, Otakar,Svatos, Ales,Masojidkova, Milena
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p. 491 - 498
(2007/10/02)
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