Marcial Moreno-Mañas

Palladium(0) nanoparticles stabilized by phosphorus dendrimers containing coordinating 15-membered triolefinic macrocycles in periphery.

A new family of phosphorus dendrimers containing on their surfaces 3, 6, 12, and 96 15-membered azamacrocycles has been synthesized. The coordinating ability of these macrocycles to palladium(0) atoms allowed the preparation of new dendrimers of several generations containing the corresponding metal complexes and several new nanoparticulated materials, where nanoparticles are stabilized mainly by the complexed dendrimers of the zero, first, and fourth generations. No reduction process of palladium(II) salts was needed to prepare nanoparticles of 2.5-7.9 nm diameter. All the new compounds and materials have been characterized by NMR, IR, elemental analysis and/or matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) spectrometry, high-resolution transmission electron microscopy, and electron diffraction. Also UV-vis spectra were obtained. The Mizoroki-Heck reaction has been catalyzed in a homogeneous and heterogeneous manner by using four different materials; in all cases, the catalyst could be recovered and reused several times.

Studies on structurally simple α,β-butenolides—I: New syntheses of racemic γ-hydroxymethyl-α,β-butenolide and derivatives

Abstract Exhaustive approaches to the synthesis of racemic γ-heterosubstituted γ-methyl-α,β-butenolides are presented, starting mainly from C 3 synthons (glyceraldehyde, glycidaldehyde, acrolein and 2,3-epoxypropyl ethers). Good general methods for the preparation of γ-hydroxymethyl-α,β-butenolide 2 , several of its ether derivatives, as well as of γ-bromomethyl-α,β-butenolide 5 , are given. The reactivities of these structurally simple but highly functionalized compounds, convenient synthons for more complex molecules, are preliminarily explored.

Palladium nanoparticles obtained from palladium salts and tributylamine in molten tetrabutylammonium bromide: their use for hydrogenolysis-free hydrogenation of olefins

Carbon-carbon double bonds have been selectively hydrogenated at room temperature in the presence of benzyloxy groups using an atmospheric pressure of hydrogen, toluene or [bmim]PF6 as the solvent and palladium nanoparticles stabilized with tetrabutylammonium bromide. The system [bmim]PF6/palladium nanoparticles can be recycled without noticeable decrease of activity.

Stereospecific preparation of ethyl (E) and (Z)-3-aryl-e-phenylpropenoates by heck reaction

Abstract Ethyl cinnamate reacts with several para -substituted aryl iodides under Jeffery-Larock conditions (Pd(OAc) 2 , NaHCO 3 , n -Bu 4 NBr, DMF, Δ) to give ethyl ( E )-3-aryl-3-phenylpropenoates as major compounds. The reaction of para -substituted ethyl cinnamates with iodobenzene under analogous conditions affords the corresponding Z isomers. The initially stereodefined alkene formed under Heck conditions undergoes a slow isomerization.

Nanosized metallic particles embedded in silica and carbon aerogels as catalysts in the Mizoroki–Heck coupling reaction

We have prepared silica, organic, and carbon aerogels doped with metallic Ni and Pd through sol-gel processes. Silica aerogel nanocomposites have been synthesized by impregnation, with Ni(acac)2 or Pd(acac)2, of the silica wet gels followed by ethanol supercritical drying. Organic aerogels were prepared by sol-gel copolymerization of formaldehyde with the potassium salt of 2,4-dihydroxybenzoic acid, followed by ion exchange with either Ni(NO3)2·6H2O or Pd(OAc)2 and CO2 supercritical drying. No special reduction step was needed. Organic aerogels were further carbonized to obtain carbon aerogels. Pd organic and carbon aerogels containing 20–40% palladium nanoparticles are good catalysts for the Mizoroki–Heck reaction.

Highly dispersed nickel and palladium nanoparticle silica aerogels: sol–gel processing of tethered metal complexes and application as catalysts in the Mizoroki–Heck reaction

Highly dispersed Ni and Pd silica aerogels were prepared through sol–gel processes. They have been synthesized by tethering the metal to the silica matrix with the use of the complexing silanes AEAPTS [N-(aminoethyl)aminopropyl]trimethoxysilane or TRIAMIN [N-((aminoethyl)aminoethyl)aminopropyl]trimethoxysilane. The gels were dried with scCO2 to afford the aerogels. High metal dispersion and small particle sizes were observed through HRTEM and XRD measurements. The organic groups were removed by oxidation and/or pyrolysis. The Pd reduced aerogels containing 15–17% of palladium are good recoverable catalysts in the Mizoroki–Heck reaction.

Superhydrophobic silica aerogels by fluorination at the gel stage

Superhydrophobic silica aerogels are obtained by surface modification of standard silica gels prepared by a two-step process with a heavily fluorinated silyl chloride followed by supercritical evacuation of the solvent.

Palladium(0) Complexes of a 15-Membered Macrocyclic Triolefin as a Recoverable Catalyst - Monomer- and Polystyrene-Anchored Versions

Preparation of the 15-membered cycle (E,E,E)-1,6,11-tris[(2,4,6-triisopropylphenyl)sulfonyl]-1,6,11-triazacyclopentadeca3,8,13-triene (8) is reported. This cyclic triolefin forms a stable Pd0 complex 9 which catalyzes several cross-coupling reactions and can be recovered. Anchoring to a polystyrene framework affords a solid version of the catalyst, which is recovered by simple filtration and reused without loss of catalytic activity.

Metal complexes in organic synthesis. : Preparation of α-(l-adamantyl)-β-dicarbonyl compounds and 4-(1-adamantyl)-3,5-disubstituted pyrazoles and isoxazoles

Abstract α-(1-Adamantyl)-β-dicarbonyl compounds are prepared by the reactions of the Co(II) complexes of β-dicarbonyl compounds with 1-bromoadamantane. This provides a route to the previously inaccessible 4-(1-adamantyl)-3.5-disubstituted pyrazoles and isoxazoles.

Pd- and Cu-catalyzed selective arylation of benzotriazole

Abstract Palladium(0)-catalyzed arylation of 1 H -1,2,3-benzotriazole (BTA) in DMF at 150° C in the presence of copper salt with arylhalides proceeds regioselectively at N-1 position. Best result has been obtained with the PdCl 2 (dppe) as catalyst and the Cu(II) phenylcyclopropylcarboxylate as co-catalyst.