Synthesis of the Chiral Fragrance Methyl Chamomile by Asymmetric Hydrogenation

An alternative synthesis of enantiomerically enriched 2-methylpentanoic butyl ester (Methyl Chamomile) is proposed. The process entails three different steps: the key one is the asymmetric hydrogenation of 2-methylenpentanoic acid catalysed by a Ru(II) complex and a chiral diphosphine

A pyridyl-triazole ligand for ruthenium and iridium catalyzed C=C and C=O hydrogenations in water/organic solvent biphasic systems

The water soluble pyridyl-triazole ligand sodium 2-(1-((pyridin-2-yl)methyl)-1H-1,2,3-triazol-4-yl) ethyl sulfate (Nal) has been successfully employed in combination with ruthenium and iridium for catalytic hydrogenation of C=C and C=O double bonds in water/toluene biphasic systems. Reaction of the ligand with [RuCl2(eta(6)-p-cymene)](2) affords the new water soluble complex [RuCl(eta(6)-p-cymene)(1)] (2) which has been found to be catalytically active in the water/organic solvent biphasic hydrogenation using styrene and 2-cyclohexen-1-one as model substrates. Very conveniently, the iridium based catalytic system is prepared by simply stirring in water [Ir(eta(4)-COD)C1]2 with Nal (Ir:Nal molar ratio-1:4), the resulting solution is catalytically active and appears more efficient than 2. With both the Ru- and Ir-based systems the catalytically active aqueous phases can be used at least three times without loss of activity. (C) 2014 Elsevier B.V. All rights reserved

New insights into the alkoxycarbonylation of propargyl alcohol

The challenging carbonylation of propargyl alcohol is effectively catalyzed by Pd(OAc)2 in combination with diphenyl-(6-methyl-pyridin-2-yl)phosphine and methanesulfonic acid. In dichloroethane at 20–50 ◦C, the reaction affords with almost complete regioselectivity alkyl 2-(hydroxymethyl)acrylates. Turnover frequency numbers (TOF) of up to 450 h−1 can be achieved working at 50 ◦C, while a maximum turnover number (TON) of about 730 is obtained at 30 ◦C. The catalyst longevity is limited because the carbonylation product reacts with the phosphorus atom of the ligand to give a quaternary phosphonium salt. This reaction leads to deactivation of the catalyst and eventually to palladium black formation

Preparation and Characterization of a Molecular Cobalt Complex Containing a Water Soluble Triazole Ligand

Cobalt(II) perchlorate hexahydrate, (Co(ClO4)2.6H2O) was reacted with a water soluble sulphonated pyridyl-triazole N,N-bidentate ligand (2-(1-((pyridine-2-yl)methyl)-1H-1,2,3-triazol-4-yl)ethyl sodium sulfate, `ligand 1.Na) in methanol to form [Co(ligand 1)2(H2O)2].4H2O as a microcrystalline solid. In this context, ligand 1.Na was first synthesized by the cycloaddition reaction of 2-(azidomethyl)pyridine and sodium 3-butyn-1-sulfate in 4:1 tert-BuOH/water solvents in presence of Cu(AcO)2H2O (10-15 mol %) as catalyst. The ligand 1.Na was white solid, absorbed moisture at open air, soluble in methanol and DMSO and characterized by elemental analysis, ESI-MS spectrum in the negative mode, 1H NMR and 13C NMR spectroscopy. In the 1H NMR spectrum of ligand 1.Na in CD3OD, a characteristic triazole strong singlet peak appeared at 7.97 ppm, a remarkable shift of δ value for CH2 proton of 2-(azidomethyl)pyridine was observed. In the 13C NMR spectrum, the triazole carbon resonates at 137.90 ppm. The prepared complex was characterized by physical data, FT-IR, ESI-MS and elemental analysis. The light pink crystals are fairly stable at open atmosphere even if they slowly loose the lattice solvent. The ESI-MS spectrum of [Co(ligand 1)2(H2O)2].4H2O indicates the species [Co(ligand 1.Na)(ligand 1)]+ and [Co(ligand 1.Na)]+ which corresponds to the m/z value at 648.6 and 402.6 respectively. Based on the observed data, octahedral geometry of the synthesized complex was suggested

A Practical, Enantioselective Synthesis of the Fragrances Canthoxal and Silvial (R), and Evaluation of Their Olfactory Activity

The fragrances (S)-(+)- and (R)-(-)-canthoxal [(S)-(+)- and (R)-(-)-3-(4-methoxyphenyl)-2-methylpropanal] and (+)- and (-)-Silvial® [(+)- and (-)-3-(4-isobutylphenyl)-2-methylpropanal] have been synthesized in high enantiopurity via a simple four-step strategy starting from the commercially available 4-substituted benzaldehydes. The key synthetic step is the catalytic asymmetric hydrogenation of the appropriate 3-aryl-2-methylacrylic acid which has been carried out employing an in situ prepared ruthenium/axially chiral phosphine catalyst (up to 98% ee). The olfactory activity of the single enantiomers has been evaluated.The fragrances (S)-(+)- and (R)-(-)-canthoxal [(S)-(+)- and (R)-(-)-3-(4-methoxyphenyl)-2-methylpropanal] and (+)- and (-)-Silvial® [(+)- and (-)-3-(4-isobutylphenyl)-2-methylpropanal] have been synthesized in high enantiopurity via a simple four-step strategy starting from the commercially available 4-substituted benzaldehydes. The key synthetic step is the catalytic asymmetric hydrogenation of the appropriate 3-aryl-2-methylacrylic acid which has been carried out employing an in situ prepared ruthenium/axially chiral phosphine catalyst (up to 98% ee). The olfactory activity of the single enantiomers has been evaluated

Synthesis of a water‑soluble thio‑triazole ligand for biphase rhodium catalyzed hydroformylation of styrene

An environmentally safe water-soluble new ligand (2-(1-(2-(methylthio)ethyl)-1H-1,2,3-triazol-4-yl)ethanol) (ligand 1) has been synthesized by the click reaction between (2-azidoethyl)(methyl)sulfane and 3-butyn-1-ol. The structure of the novel ligand was confirmed by NMR spectroscopy. In situ combination of ligand 1 with [Rh(COD)Cl]2 and [Rh (CO)2(acac)] (Rh: ligand = 1: 4) successfully employed for the biphasic catalytic hydroformylation of styrene. The formation of branched 2-phenylpropanol was confirmed by gas chromatogphic analysis. The recycled catalytic aqueous phase can be used three runs with remarkable catalytic efficiency

Biphase hydroformylation catalyzed by rhodium in combination with a water-soluble pyridyl-triazole ligand

[RhCl(COD)]2 in combination with a water soluble sulphonated pyridyl-triazolyl N,N-bidentate ligand efficiently catalyzes styrene and 1-hexene hydroformylation in water/organic solvent biphasic systems. The catalyst displays a good activity affording mixtures of linear and branched aldehydes with complete chemoselectivity. The aqueous catalytic phase may be recycled four times giving complete substrate conversion by 18 h. Mercury-poisoning experiments and transmission electron microscopy indicate that, after the first catalytic run, rhodium is present in the aqueous phase in nanoparticle form.[RhCl(COD)]2in combination with a water soluble sulphonated pyridyl-triazolyl N,N-bidentate ligand efficiently catalyzes styrene and 1-hexene hydroformylation in water/organic solvent biphasic systems. The catalyst displays a good activity affording mixtures of linear and branched aldehydes with complete chemoselectivity. The aqueous catalytic phase may be recycled four times giving complete substrate conversion by 18 h. Mercury-poisoning experiments and transmission electron microscopy indicate that, after the first catalytic run, rhodium is present in the aqueous phase in nanoparticle form

Synthesis, characterization and low temperature self assembling of (\u3b73-allyl)palladium complexes with 2-pyridyl-1,2,3-triazole bidentate ligands. Study of the catalytic activity in Suzuki-Miyaura reaction

The cationic complexes [Pd(\u3b73-C3H5)(2-((4-propyl-1H-1,2,3-triazol-1-yl)methyl)pyridine)](X) (2: X=BF4 12, 3: X=ClO4 12), and [Pd(\u3b73-2-CH3-C3H4)(2-((4-propyl-1H-1,2,3-triazol-1-yl)methyl)-pyridine)](BF4 12) (4) have been synthesized by reacting the appropriate palladium-allyl precursor with 2-((4-propyl-1H-1,2,3-triazol-1-yl)methyl)pyridine in the presence of AgBF4 or AgClO4. The solid-state structure of 2 has been determined by single-crystal X-ray diffraction analysis. According to 1H NMR spectroscopy the allyl protons undergo syn-syn, anti-anti exchange. 1H NMR spectroscopy reveals that in acetone at temperatures lower than 223 K these complexes form aggregates the stability of which is attributed to solvophobic interactions. Complex 2 is a active catalyst for the S-M coupling of aryl bromides with phenylboronic acid; good reaction rates are obtained only with activated substrates, whereas with deactivated substrates catalyst decomposition to palladium black occurs