- Intramolecular acylative ring-switching reactions of 3-(tetrahydro-2′-furyl)propanoic acid derivatives to give butanolides: Mechanism and scope
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The mechanisms by which dihydro-5-(3′-trifluoroacetoxypropyl)-2(3H)-furanone is formed when 3-(tetrahydro-2′- furyl)propanoic-trifluoroacetic mixed anhydride is treated with an acidic catalyst is defined, and routes to some potentially useful butanolide synthons are described.
- Grayson, David H.,McCarthy, Una,Roycroft, Edwin D.
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p. 1930 - 1937
(2007/10/03)
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- Radical addition of 2-iodoalkanamide or 2-iodoalkanoic acid to alkenes with a water-soluble radical initiator in aqueous media: Facile synthesis of γ-lactones
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Radical reactions in water or aqueous ethanol using a water-soluble radical initiator are described. Heating a mixture of 2-iodoacetamide and 5-hexen-1-ol in water at 75 °C in the presence of a water-soluble radical initiator, 4,4′-azobis 4-cyanopentanoic acid), afforded 5-(4-hydroxybutyl)dihydrofuran-2(3H)-one in 95% yield. The use of 2-iodoacetic acid in place of 2-iodoacetamide also gave the same γ-lactone in 93% yield. The reaction of 2-iodoacetamide with 1-octene in aqueous ethanol was initiated by 2,2′-azobis(2-methylpropanamidine) dihydrochloride to provide γ-decanolactone. Employing water as a solvent is crucial to obtain lactone in satisfactory yield.
- Yorimitsu,Wakabayashi,Shinokubo,Oshima
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p. 1963 - 1970
(2007/10/03)
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- Enantioselective synthesis of (-)-γ-jasmolactone
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The title compound was prepared in seven steps starting from the commercially available 4-ketopimelic acid. The key step features an enantioselective lactonization promoted by PPL.
- Missio,Comasseto
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p. 4609 - 4615
(2007/10/03)
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- Titanocene-Catalyzed Reduction of Lactones to Lactols
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A convenient method for the conversion of lactones to lactols is described. The hydrosilylation to lactols is carried out via air-stable titanocene difluoride or a titanocene diphenoxide precatalyst using inexpensive polymethylhydrosiloxane (PMHS) as the stoichiometric reductant. These procedures have been demonstrated with a variety of substrates and proceed in good to excellent yield.
- Verdaguer, Xavier,Hansen, Marcus C.,Berk, Scott C.,Buchwald, Stephen L.
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p. 8522 - 8528
(2007/10/03)
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- Asymmetric Synthesis of 5- and 6-Membered Lactones from Cyclic Substrates Bearing a C2-Chiral Auxiliary
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Optically active lactones were synthesized by a novel asymmetric synthesis in which enantiotopic groups remote from a prochiral center were effectively discriminated.The cyclic diamide alcohols bearing a C2-chiral auxiliary, (+)--2,2'-diamine (4), were designed and prepared such that the hydroxyl group should attack preferentially at one of the two carbonyl groups.By the catalytic action of trifluoroacetic acid, the substrates 6a,b and 19 were smoothly converted to the lactones 7a (71percent de), 7b (97percent de), and 20 (>99percent de), the configurations of whichwere determined to be R, S, and R, respectively.A naturally occurring pheromone, (R)-(+)-5-hexadecanolide (13), was synthesized optically pure from 7b.Transition-state models for the present asymmetric lactonization were constructed according to the stereoelectronic theory proposed by Deslongchamps.The stability of the models was assessed by MM2 calculation, and the direction of asymmetric induction thus calculated coincided with the experimental results.
- Yamamoto, Yukio,Sakamoto, Akio,Nishioka, Takaaki,Oda, Jun'ichi,Fukazawa, Yoshimasa
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p. 1112 - 1119
(2007/10/02)
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