13927-47-4Relevant academic research and scientific papers
Aldol condensations over reconstructed Mg-Al hydrotalcites: Structure-activity relationships related to the rehydration method
Abello, Sonia,Medina, Francesc,Tichit, Didier,Perez-Ramirez, Javier,Groen, Johan C.,Sueiras, Jesus E.,Salagre, Pilar,Cesteros, Yolanda
, p. 728 - 739 (2007/10/03)
Two different rehydration procedures in the liquid or gas phase have been applied to reconstruct mixed oxides derived from calcined hydrotalcite-like materials to be used as catalysts for aldol condensation reactions. The as-synthesized hydrotalcite, its decomposition product, as well as the reconstructed solids upon rehydration were characterized by XRD, N2 adsorption, He pycnometry, FTIR, SEM, TEM, 27Al MAS-NMR and CO 2-TPD (TPD = temperature-programmed desorption). Compared to the Mg-Al mixed oxide rehydrated in the gas phase (HT-rg), that rehydrated in the liquid phase (HT-r1) exhibits a superior catalytic performance with respect to the aldol condensation of citral with ketones to yield pseudoionones and in the self-aldolization of acetone. The textural properties of HT-r1 and HT-rg differ strongly and determine the catalytic behavior. A memory effect led to a higher degree of reconstruction of the lamellar structure when the mixed oxide was rehydrated in the gas phase rather than in the liquid phase, although liquid-phase rehydration under fast stirring produced a surface area that was 26 times greater. This contrasts to typical statements in the literature claiming a higher degree of reconstruction in the presence of large amounts of water in the medium. CO2-TPD shows that the number of OH- groups and their nature are very similar in HT-rg and HT-r1, and cannot explain the markedly different catalytic behavior. Accordingly, only a small fraction of the available basic sites in the rehydrated samples is active in liquid-phase aldol condensations. Our results support the model in which only basic sites near the edges of the hydrotalcite platelets are partaking in aldol reactions. Based on this, reconstructed materials with small crystallites (produced by exfoliation during mechanical stirring), that is, possessing a high external surface area, are beneficial in the reactions compared to larger crystals with a high degree of intraplatelet porosity.
New access to pseudo-ionones and pseudo-iso-methyl ionones from geranyl derivatives
Boulin,Arreguy-San Miguel,Delmond
, p. 1047 - 1055 (2007/10/03)
Pseudo-ionones and pseudo-iso-methyl ionones, precursors of fragrant derivatives were obtained from geranyl chloride, an industrially available starting material.
A NOVEL C10 TERPENE SYNTHON : 2-METHYL-6-METHYLENE-1,3E,7-OCTATRIENE
Mignani, G.,Morel, D.,Colleuille, Y.,Mercier, C.
, p. 2591 - 2594 (2007/10/02)
The reaction of a hydroxylated base with 3-chloro-2-methyl-6-methylene-1,7-octadiene in the presence of a palladium complex and a quaternary ammonium salt gives a novel tetraene : 2-methyl-6-methylene-1,3E,7-octatriene, which is a new C10 terpene synthon.A novel access to pseudo-ionone is also described.
Composition of pseudoionone and ionone based on the isomers of citral from the chlorotelomer of isoprene
Siirde, K. E.,Erm, A. Yu.,Vyalimyae, T. K.,Lyiveke, I. A.,Leets, K.V.
, p. 2230 - 2235 (2007/10/02)
It was shown that the synthetic isomers of citral, obtained from the monoadducts of the chlorotelomer of isoprene, only form E-enones during alkaline condensation with acetone.Under the influence of mineral acids the (3E, 5Z)- and (3E, 5E)-6,10-dimethyl-3,5,9-undecatrien-2-ones formed from the Z and E isomers of citral gave a mixture of α-, β-, and γ-ionones, hydroxyionone, and 10-hydroxypseudoionones.The isomeric (3E, 5Z)-(3E, 5E)6,8,8-trimethyl-3,5,9-decatrien-2-ones and (3E, 5E)-5,10-dimethyl-3,5,9-undecatrien-2-one, obtained from the skeletal isomers of citral, do not undergo cyclization under the indicated conditions.The isolated compounds were characterized by (13)C NMR spectroscopy.
Isomerisation cis trans regioselective de doubles liaisons trisubstituees.
Cuvigny,Herve du Penhoat,Julia
, p. 1331 - 1334 (2007/10/02)
At moderate temperatures aqueous sulphur dioxide equilibrates trisubstituted double bonds.
