Showing results 101 to 106 of 106
  Heightened selectivity in aromatic nitrations and chlorinations by the use of solid supports and catalystsDelaude, Lionel  ; Laszlo, Pierre ; 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. Detailed reference viewed: 14 (2 ULg)Acidic degradation of zeolite catalysts in the course of aromatic chlorination using sulfuryl chloride; Delaude, Lionel ; Fransolet, André-Mathieu et alin 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 ▲] Detailed reference viewed: 34 (2 ULg)Regioselective hydrochlorination of olefins is favored by an acidic solid catalystDelaude, Lionel ; Laszlo, Pierre 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 ▲] Detailed reference viewed: 28 (0 ULg)Aromatic chlorination of toluene and of anisole using clay-supported iron(III) chloride and m-chloroperbenzoic Acid - A biomimetic approachDelaude, Lionel ; Laszlo, Pierre 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 ▲] Detailed reference viewed: 46 (0 ULg)Versatility of zeolites as catalysts for ring or side-chain aromatic chlorinations by sulfuryl chlorideDelaude, Lionel ; Laszlo, Pierre 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 ▲] Detailed reference viewed: 14 (0 ULg)A procedure for quantitative regioselective nitration of aromatic hydrocarbons in the laboratoryCornélis, André ; Delaude, Lionel ; Gerstmans, André et alin 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 ▲] Detailed reference viewed: 48 (10 ULg) |
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