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Molecules, Volume 2, Issue 7 (July 1997) – 4 articles , Pages 100-113, Articles M23-M24

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43 KiB

Open AccessArticle

Amberlyst 15 Catalyzed Prenylation of Phenols: One-Step Synthesis of Benzopyrans

by G. P. Kalena, A. Jain and A. Banerji

Molecules 1997, 2(7), 100-105; https://doi.org/10.3390/20700100 - 30 Jul 1997

Cited by 44 | Viewed by 9293

Abstract

A convenient one-step synthesis of 2,2-dimethylchromans and chromenes using Amberlyst 15 as a catalyst is described. Full article

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143 KiB

Open AccessArticle

(R,R)-Tartaric Acid Dimethyl Diester from X-Ray and Ab Initio Studies: Factors Influencing Its Conformation and Packing

by Urszula Rychlewska, B. Warzajtis, M. Hoffmann and J. Rychlewski

Molecules 1997, 2(7), 106-113; https://doi.org/10.3390/20700106 - 20 Jul 1997

Cited by 28 | Viewed by 11281

Abstract

The conformation of dimethyl (R,R)-tartrate has been analyzed on the basis of the single crystal X-ray diffraction method as well as by ab-initio quantum chemical studies. The results showed that the extended T conformation containing two planar hydroxyester moieties predominates in both ab-initio and X-ray studies. The lowest energy conformer in ab-initio calculations has C₂ symmetry and hydrogen bonds between a hydroxyl group and the nearest carbonyl oxygen. The second in energetical sequence, with an energy difference of only 1.2 kcal/mol, is the asymmetrical conformer, which differs from the lowest energy form by the rotation of one of the ester groups by 180°. Intramolecular OH...O hydrogen bonds observed in this rotamer again involve only proximal functional groups. This conformer is present in the crystal structure of the studied compound, although its conformation in the solid state is no longer stabilized by intramolecular hydrogen bonds of the type mentioned above. In the crystal, hydroxyl groups are mostly involved in intermolecular hydrogen bonds and form only a weak intramolecular hydrogen bond with each other. The planar arrangement of the α-hydroxyester moieties combined with the extended conformation of the carbon chain seems to be stabilized by the intramolecular hydrogen bonds between neighboring functional groups and by the long range dipole-dipole interactions between two pairs of CO and (β)C-H bonds. Full article

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83 KiB

Open AccessShort Note

Synthesis of 3-Bromo-2-ethoxy-4-methyl-3,4-dihydro-2H-pyran-6-amide

by Jin-Cong Zhuo and Hugo Wyler

Molecules 1997, 2(7), M24; https://doi.org/10.3390/M24 - 4 Jul 1997

Viewed by 3075

Abstract

To a cooled (0[infinity]C) solution of 1 (0.68 g, 2.76 mmol) in CH₂Cl₂ (2 ml) was added successively hydrogen peroxide (30%, 1.29 ml), tetra-(n-butyl)ammonium hydrogen sulfate (187 mg) and an aqueous solution of sodium hydroxide (20%, 1.03 ml).[...] Full article

(This article belongs to the Section Molbank Section of Molecules, 1997-2001)

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