37443-42-8Relevant articles and documents
Palladium-catalyzed asymmetric hydrogenation of furan carboxylic acids
Maris, Mihaela,Huck, Wolf-Ruediger,Mallat, Tamas,Baiker, Alfons
, p. 52 - 58 (2003)
Enantioselective hydrogenation of aromatic and heteroaromatic compounds is the field where chirally modified metal hydrogenation catalysts have the biggest potential compared to homogeneous chiral transition metal complexes. Here we report the hydrogenation of furan and benzofuran carboxylic acids over a cinchonidine-modified 5 wt% Pd/Al2O3 catalyst. (S)-Tetrahydrofuran-2-carboxylic acid was synthesized in 4 h at rt and 30 bar with 95% yield and 32% ee. The ee was lower in the hydrogenation of methylfuran carboxylic acids but up to 100% de was achieved. In the slow hydrogenation of benzofuran-2-carboxylic acid, the ee went up to 50% at 29% yield. The potential application of the method is limited by the competing hydrogenation of the quinoline rings of cinchonidine in the latter reaction, necessitating the feeding of small amounts of cinchonidine during reaction. Still, this simple method using an easily available chiral modifier and catalyst affords the highest rate and ee reported so far in the catalytic asymmetric hydrogenation of furan and benzofuran carboxylic acids, and it may be an attractive route in combination with optical resolution. We assume that the reaction mechanism is analogous to that described for α,β-unsaturated carboxylic acids over the same catalyst, involving a 1:2-type interaction between the cinchonidine and the acid dimer.
Hydrogenolysis of tetrahydrofuran-2-carboxylic acid over tungsten-modified rhodium catalyst
Asano, Takehiro,Nakagawa, Yoshinao,Tamura, Masazumi,Tomishige, Keiichi
, (2020/07/04)
Catalysts for reduction of tetrahydrofuran-2-carboxylic acid (THFCA), which can be synthesized from furfural via oxidation and hydrogenation, were explored among the combinations of noble metal and reducible metal oxide supported on SiO2. Rh-WOx/SiO2 catalysts showed activity in C-O hydrogenolysis at 2-position of THFCA (to δ-valerolactone and 5-hydroxyvaleric acid) and higher yield ratio of these C-O hydrogenolysis products to carboxylic acid hydrogenation products than other bimetallic catalysts. The activity of Rh-WOx/SiO2 catalysts was highest at W/Rh = 0.25 mol/mol. XRD, TPR, CO adsorption and XAFS characterizations showed that the Rh-WOx/SiO2 (W/Rh = 0.25) catalyst contained Rh metal particles with surface modification with isolated W2+ oxide species. The mechanism that hydride-like species formed on Rh atom attacks the C atom at the α-position (2-position) of adsorbed carboxylate on W atom is proposed based on the similar kinetics and similar catalyst structure to Rh-MOx/SiO2 (M = Re, Mo) which is known to be active in THFA hydrogenolysis to 1,5-pentanediol.
Molecular features of the prazosin molecule required for activation of Transport-P
da Silva, Joaquim Fernando Mendes,Walters, Marcus,Al-Damluji, Saad,Ganellin, C. Robin
, p. 7254 - 7263 (2008/12/23)
Closely related structural analogues of prazosin have been synthesised and tested for inhibition and activation of Transport-P in order to identify the structural features of the prazosin molecule that appear to be necessary for activation of Transport-P. So far, all the compounds tested are less active than prazosin. It is shown that the structure of prazosin appears to be very specific for the activation. Only quinazolines have been found to activate, and the presence of the 6,7-dimethoxy and 4-amino groups appears to be critically important.
