4-Aminobicyclo[2.2.2]octanone Derivatives with Antiprotozoal Activities

Summary.  4-Aminobicyclo[2.2.2]octanones which were prepared in one-pot-reactions from benzylidene acetone and dialkylammonium rhodanides were reduced stereoselectively to their corresponding alcohols. The activities of the bicyclic compounds against causative organisms of tropical deseases were examined. The 4-aminobicyclo[2.2.2]octan-2-ols were in general more active against Trypanosoma b. rhodesiense and Plasmodium falciparum than the corresponding keto compounds. Corresponding author. E-mail: robert.weis@uni-graz.at Received November 27, 2002; accepted December 2, 2002 Published online May 2, 2003     

Intermediate Product–Catalyst Complexes in the Homogeneous Hydrogenation of Styrene Derivatives with Parahydrogen and Cationic RhI Catalysts

The catalyst-bound intermediate 1 is detected in the homogeneous hydrogenation of styrene derivatives in the presence of cationic Rh^I catalysts 2 . The detachment from the catalyst of the ethylbenzene 3 formed turns out to be slow and possibly rate-determining in some cases.     

Synthesis and studies of Rh(I) catalysts within and across poly(alkyl aryl ether) dendrimers

In order to study the efficiencies of catalytic moieties within and across dendrimer generations, partially and fully functionalized dendrimers were synthesized. Poly(alkyl aryl ether) dendrimers from zero to three generations, presenting 3 to 24 peripheral functionalities, were utilized to prepare as many as 12 catalysts. The dendrimer peripheries were partially and fully functionalized with triphenylphosphine in the first instance. A rhodium(I) metal complexation was performed subsequently to afford multivalent dendritic catalysts, both within and across generations. Upon synthesis, the dendritic catalysts were tested in the hydrogenation of styrene, in a substrate-to-catalyst ratio of 1:0.001. Turn-over-numbers were evaluated for each catalyst, from which significant increases in the catalytic activities were identified for multivalent catalysts than monovalent catalysts, both within and across generations.     

Homogeneous Hydrogenation Catalysis with Monodisperse,Dendrimer‐Encapsulated Pd and Pt Nanoparticles

Extraordinarily stable , monodisperse noble metal nanoparticles can be prepared by using dendrimers as both templates and stabilizers. Dendrimer‐encapsulated Pd nanoparticles (see the schematic representation) exhibit high catalytic activity for the hydrogenation of alkenes in water. The catalytic activity and selectivity of these materials can be controlled by adjusting the dendrimer generation.     

The First Efficient Hydroaminomethylation with Ammonia: With Dual Metal Catalysts and Two-Phase Catalysis to Primary Amines

Primary and unbranched secondary amines are obtained by the highly selective hydroaminomethylation of olefins with ammonia [Eq. (a)]. The selectivity is readily controlled with a new dual Rh/Ir catalyst in a two-phase system.     

Synthesis of New Thieno[2,3-<Emphasis Type="Italic">b</Emphasis>:5,4-<Emphasis Type="Italic">c</Emphasis>′]dipyridines

Summary. We describe the formation of thieno[2,3-b:5,4-c]dipyridines from 5,6-dihydropyridine-2(1H)-thiones. The two-step reaction mechanism was revealed by isolation of an intermediate. The oxo and thioxo groups of the obtained tricyclic compounds were hydrogenated selectively. The structures of all new compounds were elucidated by NMR experiments.Received December 17, 2002; accepted December 20, 2002 Published online June 2, 2003     

Kinetic Influences on Enantioselectivity for Non-Diastereopure Catalyst Mixtures

Different kinetic rate laws were observed for two diastereomeric catalysts which separately gave opposite enantioselectivities in the asymmetric hydrogenation of the dimethyl ester of itaconic acid. In reactions carried out using an equal mixture of the two catalysts, a conversion-dependent enantioselectivity was predicted from the separate reaction-rate data, in agreement with the experimentally observed final enantioselectivity of 54.8 % ee (see diagram).     

Highly Enantioselective Hydrogenation of Simple Ketones Catalyzed by a Rh–PennPhos Complex

Even alkyl methyl ketones undergo asymmetric hydrogenation with high enantioselectivity when a rhodium complex of the conformationally rigid chiral ligand 1 (Me-PennPhos; R=CH₃) is used as the catalyst. Basic additives such as 2,6-lutidine contribute to the achievement of high enantiomeric excesses.     

Enantioselective Hydrogenation of Olefins with Iridium–Phosphanodihydrooxazole Catalysts

High turnover numbers and up to 98% ee were obtained in the catalytic hydrogenation of unfunctionalized aryl-substituted olefins with iridium–phosphanyldihydrooxazole complexes 1 (see reaction scheme). The anion of the complex—for example, hexafluorophosphate or tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BARF⁻)—has a remarkable effect on the reactivity and longevity of the catalyst.     

Synthesis of Optically Active α-Amino- phosphinic Acids by Catalytic Asymmetric Hydrogenation in Organic Solvents and Aqueous Micellar Media

Enantiomeric excesses of up to 99 % could be obtained in the synthesis of the biologically interesting acylated α-aminophosphinic acids 1 (R¹=Me, Ph; R²=H, Me, Et; R³=H, F, iPr) by asymmetric hydrogenation with rhodium complex catalysts and subsequent hydrolysis [Eq. (1)]. cod=1,5-cyclooctadiene.