- Dehydrogenative lactonization of diols in aqueous media catalyzed by a water-soluble iridium complex bearing a functional bipyridine ligand
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A new catalytic system for the dehydrogenative lactonization of a variety of benzylic and aliphatic diols in aqueous media was developed. By using a water-soluble, dicationic iridium catalyst bearing 6,6′-dihydroxy-2, 2′-bipyridine as a functional ligand, highly atom economical and environmentally benign synthesis of various lactones was achieved in good to excellent yields. Recovery and reuse of the catalyst were also accomplished by a simple phase separation and the recovered catalyst maintained its high activity at least until the fifth run. Copyright
- Fujita, Ken-Ichi,Ito, Wataru,Yamaguchi, Ryohei
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p. 109 - 112
(2014/01/23)
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- Total synthesis of neo-tanshinlactones through a cascade benzannulation-lactonization as the key step
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The cascade annulation-lactonization of phthalides with α-carboxyfurylacrylates in the presence of lithium hexamethyldisilazide (LiHMDS) provides both convergent and semiconvergent regioselective syntheses of neo-tanshinlactones in moderate yields. This methodology also offers an avenue for the direct syntheses of hitherto unreported 6-alkoxycarbonyl-substituted neo-tanshinlactones and their heterocyclic analogues. A new synthesis of 4-alkyl phthalides was developed on the basis of a combination of a Duff reaction and Fuerstner cross-coupling. The cascade benzannulation-lactonization of phthalides with α-carboxyfurylacrylates was employed as the key reaction for the concise synthesis of neo-tanshinlactone. Copyright
- Ghosh, Ketaki,Karmakar, Raju,Mal, Dipakranjan
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p. 4037 - 4046
(2013/07/19)
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- Chemical oxidation of an anticonvulsant N-(5'-methylisoxazol-3-yl) 2,6- dimethylbenzamide (D2916)
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The new anticonvulsant N-(5'-methylisoxazol-3-yl)-2,6-dimethylbeazamide (D2916), which presents two kinds of methyl groups which could be oxidized, was submitted to various chemical oxidizing agents. Several sites and degrees of oxidation were observed. The main oxidized site was the arylmethyl group without cleavage of the isoxazole ring, leading via carboxylic acid and primary alcohol intermediates to phthalimide and lactame derivatives. In no case was the methyl group of the isoxazole moiety hydroxylated.
- Adolphe-Pierre,Menager,Tombret,Verite,Lepage,Lafont
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p. 513 - 518
(2007/10/03)
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- Aromatic Spiranes XXI [1]: Syntheses of Methyl Substituted Phthalaldehydic Acids and their Ethyl and Methyl Esters as Synthones for Syntheses of Methylated 2,2′-Spirobiindandiones
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The isomeric methyl phthalaldehydic acids 11 were obtained from phthalides 4 by bromation (NBS) to the 3-bromo derivatives 7 and subsequent hydrolysis with water. 4 in turn were accessible from dimethyl methyl benzoates 1 by dibromination with NBS and subsequent thermical cyclization to the bromo derivatives 3 which, on catalytic dehalogenation, afforded the phthalides 4. Reaction of 11 with methanol or ethanol gave the pseudo-esters 13 and 14, resp. Short treatment of 11 with diazomethane on the other hand yielded the methyl formyl benzoates 15b to 15e. Prolonged reaction (several hours) gave the oxiranyl compounds 17; in addition, the acetonyl derivatives 18 were also found, obviously formed by a double methylene insertion into 15. All reactions proceeded with good to excellent yields.
- Neudeck
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p. 201 - 217
(2007/10/03)
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- OXIDATION OF SUBSTITUTED 2-METHYL BENZOIC ACIDS AND ACRYLIC ACIDS BY S2O8(2-)-Ag(I); THEIR CONVERSION TO PHTHALIDES AND BUTENOLIDES THROUGH REARRANGEMENT OF ACYLOXYL RADICALS.
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Ag (I) mediated persulphate oxidation of various 2-methyl benzoic acids and acrylic acids, co-catalysed by Cu (II), leads to unsaturated γ-lactones, together with decarboxylation products.Lactonisation proceeds through 1,5 hydrogen trasfer from intermediate acyloxyl radicals.
- Bertrand, M. P.,Oumar-Mahamat, H.,Surzur, J. M.
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p. 1209 - 1212
(2007/10/02)
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- HIGHLY REGIOSELECTIVE REDUCTION OF UNSYMMETRICAL CYCLIC ANHYDRIDES TO LACTONES WITH HINDERED TRIALKYLBOROHYDRIDES
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Lithium trialkylborohydrides reduce cyclic anhydrides to the corresponding lactones in good to excellent isolated yields.With unsymmetrical anhydrides, increasing the steric requirements of the trialkylborohydride dramatically enhances the regioselectivity of the reduction of the less hindered carbonyl group of the anhydride.
- Krishnamurthy, S.,Vreeland, William B.
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p. 265 - 270
(2007/10/02)
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