References of "Delaude, Lionel"
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See detailLes strychnos africains et leurs alcaloïdes
Delaude, Clément ULg; Delaude, Lionel ULg

in Bulletin de la Société Royale des Sciences de Liège (1997), 66(4), 183-286

In the Greek Antiquity, the term strychnos was first coined to describe various toxic Solanacae. Nowadays, the genus Strychnos created by Linnaeus in 1753 is the numerically most important genus from the ... [more ▼]

In the Greek Antiquity, the term strychnos was first coined to describe various toxic Solanacae. Nowadays, the genus Strychnos created by Linnaeus in 1753 is the numerically most important genus from the Loganiaceae family and comprises 196 species growing in the warm regions of Asia (58 species), America (64) and Africa (75). Species on the three continents are almost totally segregated. Only Strychnos potatorum is common to Asia and Africa. The toxicity of Strychnos was empirically well-known from time immemorial. Inhabitants of South-Eastern Asia and India had an ancestral knowledge of Strychnos nux vomica, whose deadly poisonous seeds were later imported and marketed in Europe to kill rodents and small predators. Concentrated extracts from Amazonian Strychnos, known as curares, are also remarkable hunting poisons, used by South American Indians. Accordingly, modern scientific investigations of Strychnos and their alkaloids started with Asian or American species used as traditionnal poisons. Strychnine was the first alkaloid found in Strychnos. It was isolated from Asian S. nux vomica in 1818, but its structure was fully elucidated only in the 1950s. Meanwhile, various curarizing alkaloids from American Strychnos were identified. Based on these early results, Strychnos alkaloids were initially classified according to their geographical origin. Asian Strychnos were assumed to contain strychnine and related compounds, whereas curarizing ammonium salts were associated with American Strychnos. African species were assimilated to their Asian counterparts and deemed of less interest. During the last three decades, however, systematic screening of African Strychnos has revealed the presence of numerous, varied alkaloids in these plants and demonstrated that the correlation between geographical distribution and alkaloid content was erroneous. Presently, 47 African species have been investigated and their alkaloids analyzed, significantly more than Asian and American materials (about 10 and 20 species, respectively). In this review, we present the alkaloids isolated so far from African Strychnos. 309 structures are listed and sorted according to their molecular weight, the most useful index key in modern research based on mass spectrometry. [less ▲]

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See detailZeolite-catalyzed acetylation of alkenes with acetic anhydride
Smith, Keith; Zhenhua, Zhao; Delaude, Lionel ULg et al

in Studies in Surface Science and Catalysis (1997), 108(Heterogeneous Catalysis and Fine Chemicals IV), 99-106

Among various microporous adsorbents such as alumina, silica, clays, mol. sieves, etc., the HY zeolite was found to be best at promoting the acylation of 2,3-dimethyl-2-butene with acetic anhydride. The ... [more ▼]

Among various microporous adsorbents such as alumina, silica, clays, mol. sieves, etc., the HY zeolite was found to be best at promoting the acylation of 2,3-dimethyl-2-butene with acetic anhydride. The influence of numerous exptl. parameters on the course of the reaction was investigated. Variations in the silica/alumina ratio of the zeolite, or in the relative proportions of reagents and catalyst, markedly affected the yield of 3,3,4-trimethyl-4-penten-2-one, whereas the reaction time and temp. were less influential. The procedure was extended to various other alkenes and it was possible to regenerate and to reuse the solid catalyst without significant loss of activity. [less ▲]

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See detailA Novel Oxidizing Reagent Based on Potassium Ferrate(VI)
Delaude, Lionel ULg; Laszlo, Pierre ULg

in Journal of Organic Chemistry (1996), 61(18), 6360-6370

A new, efficient preparation has been devised for potassium ferrate(VI) (K(2)FeO(4)). The ability of this high-valent iron salt for oxidizing organic substrates in nonaqueous media was studied. Using ... [more ▼]

A new, efficient preparation has been devised for potassium ferrate(VI) (K(2)FeO(4)). The ability of this high-valent iron salt for oxidizing organic substrates in nonaqueous media was studied. Using benzyl alcohol as a model, the catalytic activity of a wide range of microporous adsorbents was ascertained. Among numerous solid supports of the aluminosilicate type, the K10 montmorillonite clay was found to be best at achieving quantitative formation of benzaldehyde, without any overoxidation to benzoic acid. The roles of the various parameters (reaction time and temperature, nature of the solvent, method of preparation of the solid reagent) were investigated. The evidence points to a polar reaction mechanism. The ensuing procedure was applied successfully, at room temperature, to oxidation of a series of alcohols to aldehydes and ketones, to oxidative coupling of thiols to disulfides, and to oxidation of nitrogen derivatives. At 75 degrees C, the reagent has the capability of oxidizing both activated and nonactivated hydrocarbons. Toluene is turned into benzyl alcohol (and benzaldehyde). Cycloalkanes are also oxidized, in significant (30-40%) yields, to the respective cycloalkanols (and cycloalkanones). Thus, potassium ferrate, used in conjunction with an appropriate heterogeneous catalyst, is a strong and environmentally friendly oxidant. [less ▲]

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See detailOxidation of organic substrates with potassium ferrate (VI) in the presence of the K10 montmorillonite
Delaude, Lionel ULg; Laszlo, Pierre ULg; Lehance, Pascal

in Tetrahedron Letters (1995), 36(46), 8505-8508

Among various aluminosilicate supports, the K10 montmorillonite clay was the best catalyst for the oxidation of organic substrates with potassium ferrate (VI). Thus, a solid mixture of K2FeO4 and K10 has ... [more ▼]

Among various aluminosilicate supports, the K10 montmorillonite clay was the best catalyst for the oxidation of organic substrates with potassium ferrate (VI). Thus, a solid mixture of K2FeO4 and K10 has been used for the efficient oxidation of selected alcohols, benzylamine, thiophenol, and aniline in hydrocarbon solvents at room temperature. Somewhat humid clay performs best, and it is important to control the amount of water associated to the solid support. [less ▲]

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See detailCoupling and carbonylation of iodoaromatics and terminal alkynes or alkynols catalyzed by a dimeric palladium hydroxide
Delaude, Lionel ULg; Masdeu, Anna M.; Alper, Howard

in Synthesis (1994), (11), 1149-1151

The palladium(II) complex [(Ph(3)P)Pd(Ph)mu-OH)](2) is an effective catalyst for the coupling and carbonylation of alkynes and iodoarenes to give acetylenic ketones in 63-94% yields. Acetylenic hydroxy ... [more ▼]

The palladium(II) complex [(Ph(3)P)Pd(Ph)mu-OH)](2) is an effective catalyst for the coupling and carbonylation of alkynes and iodoarenes to give acetylenic ketones in 63-94% yields. Acetylenic hydroxy ketones were formed using secondary or tertiary alkynols as reactants. [less ▲]

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See detailGeometric control of a pyridoxal-catalyzed aldol condensation
Koh, John T.; Delaude, Lionel ULg; Breslow, Ronald

in Journal of the American Chemical Society (1994), 116(25), 11234-11240

A chiral cyclophane derivative of pyridoxal has been synthesized that has amino groups oriented specifically over one face of the cofactor. The compound catalyzes the formation of threonine and allo ... [more ▼]

A chiral cyclophane derivative of pyridoxal has been synthesized that has amino groups oriented specifically over one face of the cofactor. The compound catalyzes the formation of threonine and allo-threonine from glycine and acetaldehyde with enantioinductions that are a function of pH, reversing the optical selectivity between low pH and high pH. The stereochemical results are compared with those of structurally related pyridoxal cyclophanes that lack titratable catalytic groups. Explanations are advanced for this stereochemical reversal and for the otherwise surprising preference of most of these compounds to react on the more hindered face of the pyridoxal. Models indicate that the transamination intermediate is distorted by the transannular chain, and stereoelectronic arguments predict that this distortion should lead to reaction on the face that carries the chain, as observed. The stereochemical reversal with the attached (dimethylamino)alkyl group, as a function of pH, may reflect catalysis by the protonated form, but metal coordination by the basic form cannot be excluded. [less ▲]

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See detailSolid-state nuclear magnetic resonance studies of the transformation of the zeolite Y catalyst in the course of hydrochlorination of 1-methylcyclohexene by thionyl chloride
Kolodziejski, Waclaw; Delaude, Lionel ULg; Laszlo, Pierre ULg et al

in Applied Catalysis A : General (1993), 98(1), 71-79

1-Methylcyclohexene was hydrochlorinated with SOCl2 to 1-chloro-1-methylcyclohexane at room temperature in CH2Cl2 as the solvent and in presence of the faujasitic zeolite ZF520 catalyst. 4-Coordinated ... [more ▼]

1-Methylcyclohexene was hydrochlorinated with SOCl2 to 1-chloro-1-methylcyclohexane at room temperature in CH2Cl2 as the solvent and in presence of the faujasitic zeolite ZF520 catalyst. 4-Coordinated framework aluminium in the parent sample coexisting with a small amount of immobile extra-framework aluminium at ca. -1 ppm is completely removed after just one reaction run and transformed into two distinct 6-coordinated species resonating at 0.2 and -3.1 ppm. The former line is assigned to Al(H2O)63+ cations, the latter is likely to come from a species with mixed solvation shells, probably Al(Cl-)(H2O)52+ and Al(OH-)(H2O)52+. Crystallinity of the catalyst is seriously affected by the reaction. The spectra confirm that before reaction the zeolite contains Si(3Si,1OH) and Si(2Si,2OH) groups. During the reaction most hydroxyl groups created by dealumination are removed, although some Si(3Si,1OH) remain. MAS NMR spectra are fully consistent with the proposed reaction mechanism. [less ▲]

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See detailHeightened selectivity in aromatic nitrations and chlorinations by the use of solid supports and catalysts
Delaude, Lionel ULg; Laszlo, Pierre ULg; Smith, Keith

in Accounts of Chemical Research (1993), 26(12), 607-613

The heightened selectivity in aromatic nitrations and chlorinations using solid supports and catalysts is reviewed with 67 references.

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See detailAcidic degradation of zeolite catalysts in the course of aromatic chlorination using sulfuryl chloride
Antenucci, Diano; Delaude, Lionel ULg; Fransolet, André-Mathieu ULg et al

in Journal of Catalysis (1992), 135(1), 92-98

The structural changes of two faujasite type zeolites in the course of aromatic chlorinations by sulfuryl chloride, SO2Cl2, were investigated by X-ray powder diffraction. Both catalysts examined, the NaX ... [more ▼]

The structural changes of two faujasite type zeolites in the course of aromatic chlorinations by sulfuryl chloride, SO2Cl2, were investigated by X-ray powder diffraction. Both catalysts examined, the NaX zeolite, which promotes catenar side-chain chlorination, and the ZF520 zeolite, which promotes nuclear electrophilic chlorination, are strongly altered in the acidic reaction medium (hydrochloric acid and sulfur dioxide are evolved continually as the reaction proceeds). In the presence of residual humidity, progressive dealumination of the ZF520 catalyst occurs without destruction of the zeolite framework. It gives rise to the formation of an alum type structure, for which the molecular formula (H3O)Al(SO4)2.12 H2O has been suggested. Rapid degradation of the NaX zeolite is accompanied by the formation of sodium chloride and of the sodium aluminium sulfate hexahydrate, NaAl(SO4)2.6 H2O. These compounds indeed catalyze the side-chain chlorination of toluene by SO2Cl2. Under water exclusion, structural degradation of both zeolites is slowed down; formation of hydrated sulfates is prevented; however the efficiency of the catalysts is also reduced. [less ▲]

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See detailRegioselective hydrochlorination of olefins is favored by an acidic solid catalyst
Delaude, Lionel ULg; Laszlo, Pierre ULg

in Tetrahedron Letters (1991), 32(30), 3705-3708

With thionyl chloride SOCl2 as HCl precursor, 1-methylcyclohexene is hydrochlorinated. In the absence of a solid catalyst, between half and two-thirds of the product mixture are the anti-Markovnikov ... [more ▼]

With thionyl chloride SOCl2 as HCl precursor, 1-methylcyclohexene is hydrochlorinated. In the absence of a solid catalyst, between half and two-thirds of the product mixture are the anti-Markovnikov adduct, trans 1-chloro-2-methyl cyclohexane. Catalysis by the ZF 520 zeolite or the K10 montmorillonite makes the reaction selective. It then affords a quantitative yield of (10:1) Markovnikov adduct 1-chloro-1-methylcyclohexane. [less ▲]

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See detailAromatic chlorination of toluene and of anisole using clay-supported iron(III) chloride and m-chloroperbenzoic Acid - A biomimetic approach
Delaude, Lionel ULg; Laszlo, Pierre ULg

in Catalysis Letters (1990), 5(1), 35-44

n the presence of meta-chloroperbenzoic acid, clay-supported ferric chloride is an efficient aromatic chlorinating agent for toluene and anisole. Influence of various experimental factors such as the ... [more ▼]

n the presence of meta-chloroperbenzoic acid, clay-supported ferric chloride is an efficient aromatic chlorinating agent for toluene and anisole. Influence of various experimental factors such as the nature of the solvent, the peracid or the metallic cation were investigated. These reactions represent a laboratory equivalent to biological halogenations through oxidation of halide ions by peroxidases in the presence of hydrogen peroxide. [less ▲]

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See detailVersatility of zeolites as catalysts for ring or side-chain aromatic chlorinations by sulfuryl chloride
Delaude, Lionel ULg; Laszlo, Pierre ULg

in Journal of Organic Chemistry (1990), 55(18), 5260-5269

Zeolites catalyze chlorination of aromatics by sulfuryl chloride SO2Cl2. It is possible by an appropriate choice of the catalyst to effect at will, with very high selectivity, either the ring or the side ... [more ▼]

Zeolites catalyze chlorination of aromatics by sulfuryl chloride SO2Cl2. It is possible by an appropriate choice of the catalyst to effect at will, with very high selectivity, either the ring or the side-chain chlorination. Zeolite ZF520 is the choice catalyst for the former, because of its high Brønsted acidity. Zeolite NaX (13X) is a fine catalyst for the latter, free-radical chlorination; the reaction is best effected in the presence of a light source; the catalyst can be re-used many times with no loss in activity. Both reaction modes, the ionic (ring chlorination) and the radical (side-chain substitution), are likely to occur outside of the channel network in the microporous solid. The effects of various experimental factors -such as the nature of the solvent, the reaction time and temperature, the Brønsted acidity of the solid support, the presence of radical inhibitors, the quantity of catalysts- were investigated. The procedures resulting from this study are very easy to implement in practice and are quite effective. [less ▲]

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See detailA procedure for quantitative regioselective nitration of aromatic hydrocarbons in the laboratory
Cornélis, André ULg; Delaude, Lionel ULg; Gerstmans, André ULg et al

in Tetrahedron Letters (1988), 29(44), 5657-5660

Aromatic hydrocarbons are nitrated by metallic nitrates impregnated on the K10 montmorillonite in the presence of acetic anhydride (Menke conditions). The influence on this stoichiometric reaction of the ... [more ▼]

Aromatic hydrocarbons are nitrated by metallic nitrates impregnated on the K10 montmorillonite in the presence of acetic anhydride (Menke conditions). The influence on this stoichiometric reaction of the conditions (metallic cation; solvent; temperature) is studied. With toluene as the test molecule, the reaction is optimized to a 100% yield combined with a 8:1 para preference (79% para, 20% ortho, 1% meta). [less ▲]

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