Luis Velasco

Stable preformed chiral palladium catalysts for the one-pot asymmetric reductive amination of ketones.

The application of air stable preformed [(R)-BINAP]PdBr2, [(S)-BINAP]PdBr2, [(R)-Tol-BINAP]PdBr2, and [(S,S)-CHIRAPHOS]PdBr2 complexes in the one-pot asymmetric reductive amination of various carbonyl compounds, leading to chiral amines in very good yields with high enantioselectivities (<99% ee), is reported.

A Direct Synthesis of Aromatic Nitriles from Aldehydes Using a Mexican Bentonite and Microwave or Infrared Irradiation, in Absence of Solvent

Abstract An efficient and simple procedure for the direct conversion of aromatic Aldehydes into the corresponding nitriles with hydroxylamine hydrochloride and a Mexican Bentonite via infrared or microwave irradiation.

Clay-mediated cyclooligomerization of olefin oxides: a one-pot route to crown ethers

The catalytic synthesis of substituted 1,3-dioxolanes, 1,4-dioxanes, 9-crown-3, 12-crown-4 and 15-crown-5 ethers, from alkyl oxiranes and a montmorillonite type clay is discussed.

1,3-dioxolane formation with a montmorillonite-type clay catalyst

Abstract The coupling reaction of oxiranes with carbonyl compounds to produce 1,3-dioxolanes was promoted by catalytic amounts of a bentonitic clay. The product yield was found to be dependent on the catalyst, the reaction temperature and the reagent concentrations. A kinetic study performed with acetone and ethylene oxide showed a first-order dependence in both reagents. Other experiments made with different epoxides, carbonyl compounds and catalysts are also discussed.

Hydrodimerization of Cyclic α, β Unsaturated Ketones Promoted by Samarium Iodide

Abstract An example of hydrodimerization of some cyclic enones by SmI2/THF system is described. The use of HMPA (hexamethyl phosphoramide), as a copromoter in the system, improves the yield of dimerized products. The X-ray structure of one of these dimers, bis-3,3′(3,5,5-trimethyl cyclohexanone), is also reported.

Hydroformylation versus hydrocarboxylation of cyclohexene under homogeneous WGSR conditions: The study of Co2(CO)8 diphos/THF-H2O system

Abstract The catalytic system Co 2 (CO) 8 /diphos/THF-H 2 O, an effective catalyst for carbonylation reactions, was studied for simultaneous hydrocarboxylation and hydroformylation of cyclohexene. Using this catalytic system, cyclohexene with CO and H 2 O gives cyclohexenecarboxaldehyde and cyclohexenecarboxylic acid as the main reaction products and cyclohexylmethanol as by-product. The catalytic reaction shows that the hydrocarboxylation/hydroformylation ratio is dependent on water concentration and the reaction temperature. The effects of the other reaction variables such as CO pressure and catalyst concentration were also examined.

Characterization of a novel [Sm(HMPA)4I2]I complex by positive ion fast atom bombardment and high resolution mass spectrometry

Abstract A positive-ion Fast Atom Bombardment (FAB) study was performed to determine the structure of samarium(III) triiodine complex (I). Collision Induced Dissociation (CID) and High Resolution Mass Spectrometry were used to establish the fragmentation pattern of the C24H72O4N12P4I3Sm compound. The structure of (I) was confirmed by X-ray analysis.

Cyclo- and hydrodimerization of α,β-unsaturated ketones promoted by samarium diiodide

Samarium(II) iodide is a strong one-electron transfer reducing agent, and is effective for the cyclo- and hydrodimerization of cyclic and non-cyclic α,β-unsaturated ketones. The title dimers can easily be prepared in good yields at room temperature under neutral conditions, using two-mole equivalent of SmI2 per mole of starting substrate. The reaction is stereocontrolled. The absence of an alcohol as a proton source is essential in the process and the use of HMPA as a copromoter improves the yield of dimeric products, making the reaction regioselective over the competitive CC double bond reduction. The crystal structures of some of the dimeric derivatives are reported. When η2- or η4-iron-coordinated α,β-unsaturated ketones are used as substrates, the reaction gives mainly the 1,4-reduced products.

Characterization and X-ray crystal structure of butanoylsalophencobalt(III)

The synthesis and characterization of the pentacoordinated butanoylsalophencobalt(III) compound, including X-ray analysis, are described. The chemical shift in the 13C-n.m.r. of the carbonyl carbon was determined by means of an HMBC experiment. Collision induced dissociation (CID) and high resolution mass spectrometry were used to establish the fragmentation pattern of the CoC24H21N2O3 compound. X-ray diffraction analysis shows the presence of two conformations for the acylsalophen ligand system in the same monocrystal, as well as two different OċċċH–C hydrogen bonds with unusual interactions.

Diastereo- and enantioselective reductive amination of cycloaliphatic ketones by preformed chiral palladium complexes

An efficient preformed chiral palladium catalyzed direct diastereo- and enantioselective reductive amination of un- and substituted cycloaliphatic ketones with primary aryl amines has been developed.