2021-28-5Relevant articles and documents
Chitosan as biosupport for the MW-assisted synthesis of palladium catalysts and their use in the hydrogenation of ethyl cinnamate
Raspolli Galletti, Anna Maria,Antonetti, Claudia,Bertoldo, Monica,Piccinelli, Fabio
, p. 95 - 101 (2013)
A novel catalytic system based on palladium supported on chitosan was synthesized adopting a MW-assisted process. This synthetic approach results efficient under mild reaction conditions and very short microwave irradiation times. The prepared catalyst was employed in the hydrogenation of ethyl cinnamate (EC) to ethyl hydrocinnamate (EHC) adopting both traditional heating and MW irradiation: this is the first study on this reaction which involves this type of catalyst. In addition, a one pot fully MW-assisted process which provides the synthesis of the Pd/chitosan catalyst and its direct use in the hydrogenation of ethyl cinnamate has been also studied. This one pot procedure assures fast reaction rate under mild reaction conditions avoiding the catalyst's isolation and purification, thus making easier the reaction scale-up. The achieved yields in the target product are particularly good and the system results completely recyclable, due to the stabilizing effect of the functionalized natural support toward the palladium particles.
Peripherally cyclometalated iridium complexes of dipyridylporphyrin
Yoshida, Keita,Nakashima, Takumi,Yamaguchi, Shigeru,Osuka, Atsuhiro,Shinokubo, Hiroshi
, p. 8773 - 8775 (2011)
Two types of novel iridium pincer complexes bearing a porphyrin backbone were synthesized and characterized from dipyridylporphyrin. One of the complexes has a Lewis acidic site on the iridium center in the mer-coordination mode. The other complex takes the fac-coordination, which is rarely observed in benzene-based pincer complexes. The Royal Society of Chemistry 2011.
A Simple, Effective, New, Palladium-Catalyzed Conversion of Enol Silanes to Enones and Enals
Larock, Richard C.,Hightower, Timothy R.,Kraus, George A.,Hahn, Pat,Zheng, Deye
, p. 2423 - 2426 (1995)
Enol silanes derived from aldehydes and ketones are readily converted to the corresponding α,β-unsaturated carbonyl compounds by 10percent Pd(OAc)2 in the presence of one atmosphere of oxygen in DMSO as the solvent.
A mild method for protodesilylation of α-dimethylphenylsilyl ester substrates
Poliskie, G. Michelle,Mader, Mary M.,Van Well, Renate
, p. 589 - 592 (1999)
Mild conditions (1.2 eq. Hg(OAc)2, 1.2 eq. TBAF in 1:1 MeOH/THF; 35 min at 0 °C) have been developed for the protodesilylation of α- dimethylphenylsilyl esters. An enolate-dependent mechanism for the reaction was supported through studies indicating the clean incorporation of deuterium. To further investigate the mechanism, the optimal conditions as well as the kinetics of the reaction were explored.
Synthesis of flavor compound ethyl hydrocinnamate by Yarrowia lipolytica lipases
Zieniuk, Bart?omiej,Fabiszewska, Agata,Wo?oszynowska, Ma?gorzata,Bia?ecka-Florjańczyk, Ewa
, p. 455 - 464 (2021)
Two biocatalysts with high lipolytic activity were obtained–freeze-dried supernatant and freeze-dried biomass of Yarrowia lipolytica KKP 379. The biocatalysts were compared with Candida antarctica lipase B in the synthesis of ethyl hydrocinnamate–a flavour compound with a floral-honey aroma. Ester synthesis was completed after 2 h when 3 grams of freeze-dried biomass was used. Using smaller amounts of biomass (1.2 and 0.6 g) also allowed to achieve high ester conversion and results were comparable with those obtained for CALB used as a catalyst. Freeze-dried supernatant showed a weaker lipase activity (22.17 U/g) compared to freeze-dried biomass (46.13 U/g), which resulted in a lower conversion of 3-phenylpropionic acid to its ethyl ester, and after 36 h a conversion peaked at around 70%, then began to decrease and finally the conversion reached 50%. Moreover, antimicrobial and antioxidant properties of the synthesised ester were evaluated. Ethyl hydrocinnamate showed no antibacterial activity and weak antioxidant activity towards DPPH radical. In contrast to bacteria, the obtained compound moderately inhibited the growth of tested yeast species, where inhibition zones ranged from 10 to 16 mm.
Structural features and catalytic reactivity of [Pd{(Ph2P)2N(CH2)3Si(OCH3)3-κP,P′}I2] and related complexes in hydroalkoxycarbonylation and Suzuki–Miyaura C?C cross-coupling reactions
Stamatopoulos, Ioannis K.,Kapsi, Maria,Roulia, Maria,Vougioukalakis, Georgios C.,Raptopoulou, Catherine P.,Psycharis, Vassilis,Kostas, Ioannis D.,Kollár, László,Kyritsis, Panayotis
, p. 292 - 298 (2018)
The synthesis, as well as the structural and spectroscopic characterization of the palladium(II) complex [Pd{(Ph2P)2N(CH2)3Si(OCH3)3-κP,P′}I2], bearing the bis(phosphino)amine ligand (P,P) = (Ph2P)2N(CH2)3Si(OCH3)3, is described. X-ray crystallography studies revealed a square planar PdP2I2 coordination sphere, the structural features of which are compared with those of analogous nickel(II), palladium(II) and platinum(II) complexes. The three complexes [Pd(P,P)X2], X = Cl, Br, I, along with [Pd{(Ph2P)2N((S)-CHPhMe)-κP,P′}Cl2] and [Pd{(Ph2PSe)(Ph2P)N((S)-CHMePh)-κP,Se}Cl2], were tested as catalysts in homogeneous hydroalkoxycarbonylation reactions. The hydroalkoxycarbonylation of styrene proved to be perfectly regioselective towards the branched ester. Complex [Pd(P,P)Cl2] showed remarkably higher activity compared with that of [Pd(P,P)X2], X = Br, I. Furthermore, complex [Pd(P,P)I2] was studied as a homogeneous catalyst precursor in the Suzuki–Miyaura C?C coupling reaction between aryl bromides and phenylboronic acid. Complex [Pd(P,P)I2] was immobilized onto STx–1 montmorillonite clay and the catalytic reactivity of the heterogenized catalyst was also investigated in both hydroalkoxycarbonylation and Suzuki–Miyaura reactions.
Palladium(0) nanoparticles on glass-polymer composite materials as recyclable catalysts: A comparison study on their use in batch and continuous flow processes
Mennecke, Klaas,Cecilia, Raul,Glasnov, Toma N.,Gruhl, Susanne,Vogt, Carla,Feldhoff, Armin,Vargas, M. A. Larrubia,Kappe, C. Oliver,Kunz, Ulrich,Kirschninga, Andreas
, p. 717 - 730 (2008)
Palladium particles were generated by reduction of palladate anions bound to an ion exchange resin inside microreactors. The size and distribution of the palladium particles differed substantially depending on the degree of cross-linking and the density of ion exchange sites on the polymer/glass composites, the latter parameter having a larger influence than the former. The polymer phase of the composite materials was used for the loading with clusters composed of palladium particles which are 1 to 10 nm in diameter. The reactivity and stability of six different palladium-doped polymer/glass composite samples for transfer hydrogenations was investigated both under conventional and microwave heating in the batch mode as well as under continuous flow conditions using the cyclohexene-promoted transfer hydrogenation of ethyl cinnamate as a model reaction. Regarding the heating method it was found that catalysts that are composed of larger metal particles perform better under microwave irradiating conditions whereas samples with smaller particle sizes perform better under conventional heating. Comparing batch experiments with flow-through experiments the latter technique gives better conversion. Reusability was better in microwave heated experiments than in traditional heating.
Synthesis of Carboxylic Acids and Esters Using Polymer-Bound Oxazolines
Colwell, Arthur R.,Duckwall, Louis R.,Brooks, Reda,McManus, Samuel P.
, p. 3097 - 3102 (1981)
2,4-Dimethyl-4-(hydroxymethyl)-2-oxazoline was attached to cross-linked polystyrene, giving the polymer-bound oxazoline 3.Alkylation of 3, followed by hydrolysis or ethanolysis, provided α and α,α' mono- and dialkylated acetic acids or their ethyl esters
Catalyst type and concentration dependence in catalytic transfer hydrogenolysis of α,β-unsaturated carbonyls and nitriles via ammonium formate
Ram,Spicer
, p. 2683 - 2690 (1992)
The catalytic reduction of a variety of α,β-unsaturated compounds into saturated analogs in the presence of other reducible moieties is described using ammonium formate as a hydrogen source. The rate dependence on the concentration of Pd-C catalyst as well as on 5% Pd-BaSO4 and Ra-Ni are also characterized.
The relative reactivities of various unsaturated compounds towards diisopropyloxy(η2-cyclopentene)titanium
Cadoret, Frédéric,Six, Yvan
, p. 5491 - 5495 (2007)
Competition experiments were performed by adding pre-formed solutions of diisopropyloxy(η2-cyclopentene)titanium in diethyl ether to various mixtures of unsaturated compounds at low temperature, establishing the following reactivity scale: aldehyde > nitrile > ketone > terminal alkyne > internal alkyne > terminal alkene > ester, carbonate.
