Application of 13C N.M.R. in a re-examination of the isopropylidenation of -ribose diethyldithioacetal and erythritol

Aslani-Shotorbani, Gaffar; Buchanan, J. G.; Edgar, Alan R.; Henderson, Douglas; Shavidi, Parvin

doi:10.1016/s0040-4039(00)77840-3

Cited by 19 publications

(1 citation statement)

References 11 publications

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“…2 [33,34]. The products were identified by comparison with published 1 H and 13 C NMR data [35][36][37][38][39]. [33,34] A representative 1 H NMR spectrum of the bis-ketal (3b), ketal-ether (4b) product mixture from the Amberlite-15 catalyzed reaction of meso-erythritol (1), with acetone (2b) is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

A comparison of homogeneous and heterogeneous Brønsted acid catalysts in the reactions of meso-erythritol with aldehyde/ketones

et al. 2019

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Section: Resultsmentioning

confidence: 99%

A comparison of homogeneous and heterogeneous Brønsted acid catalysts in the reactions of meso-erythritol with aldehyde/ketones

et al. 2019

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Synthesis of Enantiomerically Pure Ferrocenes from Glycofuranosyl‐cyclopentadienes, synthetic equivalents of (alkoxyalkyl)fulvenes

Vedø¹,

Chauvin²,

Li³

et al. 1994

Helvetica Chimica Acta

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Cyclopentadienyl C-glycosides ( = glycosyl-cyclopentadienes) have been prepared as latent fulvenes. Their reaction with nucleophiles leads to cyclopentadienes substituted with (protected) alditol moieties and, hence, to enantiomerically pure metallocenes. Treatment of 1 with cyclopentadienyl anion gave the epimeric glycosyl-cyclopentadienes 6/7 (Scheme 1). Each epimer consisted of a ca. 1:l mixture of the 1,3-and 1,4-cyclopentadienes a and b, respectively, which were separated by prep. HPLC. Slow regioisomerisation occurred at room temperature. Diels-Alder addition of N-phenylmaleimide to 6a/b cu. 3 :7 at room temperature yielded three 'endo'-adducts, i.e., a disubstituted alkene (8 or 9,25%) and the trisubstituted alkenes 10 (45%) and 11 (13 %). The structure of 10 was established by X-ray analysis. Reduction of 6/7 (after isolation or in situ) with LiA1H4 gave the cyclopentadienylmannitols 12a/b (80%) which were converted to the silyl ethers 13a/b (Scheme 2). Lithiation of 13a/b and reaction with FeC1, or TiCI, led to the symmetric ferrocene 14 (76%) and the titanocene 15 (34%), respectively. The mixed ferrocene 16 (63 %) was prepared from 13a/b and pentamethylcyclopentadiene. Treatment of 6/7 with PhLi at -78" was assigned on the basis of a conformational analysis. The reaction of the ribofuranose 24 with cyclopentadienylsodium led to the epimeric C-glycosides 27a/b and 28a/b (57%, ca. 1 :I, Scheme 3 ) . The in-situ reduction of 27/28 with LiAIH, followed by isopropylidenation gave 25a/b (65%) which were transformed into the ferrocene 26 (79 %) using the standard method. Phenylation of 27/28, desilylation, and isopropylidenation gave a 20: 1 mixture of 33a/b and 34a/b (86%) which was separated by prep. HPLC. The same mixture was obtained upon phenylation of the fulvene 32 which was obtained in 36% yield from the reaction of the aldehyde-ribose 30 with cyclopentadienylsodium at -100". Lithiation of 33/34 and reaction with FeCI, gave the symmetric ferrocene 35 (88%). Similarly, the aldehyde-arabinose 36 was transformed via the fulvene 37 (32%) into a 18 :1 mixture of 38a/b and 39a/b (78 YO) and, hence, into the ferrocene 40 (83 %). Conformational analysis allowed to assign the configuration of 3S35, whereas an X-ray analysis of 40 established the (lS)-configuration of 38a/b and 40. The opposite configuration at C(1) of 38a/b and 33a/b was established by chemical degradation (Scheme 4 ) . Hydrogenation (+ 41 and 44, resp.), deprotection (+ 42 and 45, resp.), NaIO, oxidation, and NaBH, reduction yielded ( Monocyclopentadienyl titanium [ 191, zirconium [20], and hafnium [20] complexes possessing carbohydrate-derived alkoxy ligands have been used in stoichiometric amounts for the highly enantioselective addition of alkyl [20] [21] and ally1 groups [20-231 and of ester enolates [20-221 [24] to aldehydes. Zirconocenes have been used for the ring

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A simple ¹H N.m.r. Method for the quantitation of O‐acetate ester and pyruvic acid acetal content of polymeric xanthan gum and related polysaccharides

Kennedy¹,

Stevenson²,

White³

et al. 1984

Brit. Poly. J.

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Traditional methods for the quantitation of O‐acetate ester and pyruvic acid acetal in xanthan gums require hydrolysis procedures followed by determination of acetic acid and pyruvic acid separately either by colorimetric, enzymic or chromatographic assays. Some of these assays are time‐consuming and involve many solvent extractions, and during the course of these procedures the xanthan sample is destroyed by hydrolysis. The methyl protons of both O‐acetate ester and pyruvic acid acetal can be detected by 1H n.m.r. spectroscopy, and this paper describes a method for the quantitative determination of these groups on intact polymeric xanthan using an internal integration standard dissolved within the sample. The method is non‐destructive, can be easily performed on a 60MHz spectrometer equipped with Fourier Transformation and variable temperature control, and simultaneously quantitates both O‐acetate ester and pyruvic acid acetal with improved accuracy.

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Application of 13C N.M.R. in a re-examination of the isopropylidenation of -ribose diethyldithioacetal and erythritol

Cited by 19 publications

References 11 publications

A comparison of homogeneous and heterogeneous Brønsted acid catalysts in the reactions of meso-erythritol with aldehyde/ketones

A comparison of homogeneous and heterogeneous Brønsted acid catalysts in the reactions of meso-erythritol with aldehyde/ketones

Synthesis of Enantiomerically Pure Ferrocenes from Glycofuranosyl‐cyclopentadienes, synthetic equivalents of (alkoxyalkyl)fulvenes

A simple ¹H N.m.r. Method for the quantitation of O‐acetate ester and pyruvic acid acetal content of polymeric xanthan gum and related polysaccharides

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Application of 13C N.M.R. in a re-examination of the isopropylidenation of -ribose diethyldithioacetal and erythritol

Cited by 19 publications

References 11 publications

A comparison of homogeneous and heterogeneous Brønsted acid catalysts in the reactions of meso-erythritol with aldehyde/ketones

A comparison of homogeneous and heterogeneous Brønsted acid catalysts in the reactions of meso-erythritol with aldehyde/ketones

Synthesis of Enantiomerically Pure Ferrocenes from Glycofuranosyl‐cyclopentadienes, synthetic equivalents of (alkoxyalkyl)fulvenes

A simple 1H N.m.r. Method for the quantitation of O‐acetate ester and pyruvic acid acetal content of polymeric xanthan gum and related polysaccharides

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A simple ¹H N.m.r. Method for the quantitation of O‐acetate ester and pyruvic acid acetal content of polymeric xanthan gum and related polysaccharides