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Iridium Catalyst (iridium + catalyst)
Selected AbstractsEnantioselective Allylation of Aromatic Amines After in situ Generation of an Activated Cyclometalated Iridium Catalyst.CHEMINFORM, Issue 1 2005Chutian Shu Abstract For Abstract see ChemInform Abstract in Full Text. [source] On Water and in Air: Fast and Highly Chemoselective Transfer Hydrogenation of Aldehydes with Iridium Catalysts.CHEMINFORM, Issue 6 2007Xiaofeng Wu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Borrowing Hydrogen: Indirect "Wittig" Olefination for the Formation of C,C Bonds from AlcoholsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2006Phillip J. Black Abstract The successful development of an indirect three-step domino sequence for the formation of C,C bonds from alcohol substrates is described. An iridium-catalysed dehydrogenation of alcohol 1 affords the intermediate aldehyde 2. The desired C,C bond can then be formed by a facile Wittig olefination, yielding the intermediate alkene 3. In the final step the alkene is hydrogenated to afford the indirect Wittig product, the alkane 4. The key to this process is the concept of borrowing hydrogen; hydrogen removed in the initial dehydrogenation step is simply borrowed by the iridium catalyst. Functioning as a hydrogen reservoir, the catalyst facilitates C,C bond formation before subsequently returning the borrowed hydrogen in the final step. Herein we present full details of our examination into both the substrate and reaction scope and the limitations of the catalytic cycle. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Highly Enantioselective Hydrogenation of Quinoline and Pyridine Derivatives with Iridium-(P-Phos) CatalystADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2010Wei-Jun Tang Abstract The use of a chiral iridium catalyst generated in situ from the (cyclooctadiene)iridium chloride dimer, [Ir(COD)Cl]2, the P-Phos ligand [4,4,-bis(diphenylphosphino)-2,2,,6,6,-tetramethoxy-3,3,-bipyridine] and iodine (I2) for the asymmetric hydrogenation of 2,6-substituted quinolines and trisubstituted pyridines [2-substituted 7,8-dihydroquinolin-5(6H)-one derivatives] is reported. The catalyst worked efficiently to hydrogenate a series of quinoline derivatives to provide chiral 1,2,3,4-tetrahydroquinolines in high yields and up to 96% ee. The hydrogenation was carried out at high S/C (substrate to catalyst) ratios of 2000,50000, reaching up to 4000,h,1 TOF (turnover frequency) and up to 43000 TON (turnover number). The catalytic activity is found to be additive-controlled. At low catalyst loadings, decreasing the amount of additive I2 was necessary to maintain the good conversion. The same catalyst system could also enantioselectively hydrogenate trisubstituted pyridines, affording the chiral hexahydroquinolinone derivatives in nearly quantitative yields and up to 99% ee. Interestingly, increasing the amount of I2 favored high reactivity and enantioselectivity in this case. The high efficacy and enantioselectivity enable the present catalyst system of high practical potential. [source] Iridium-Catalyzed Selective Synthesis of 4-Substituted Benzofurans and Indoles via Directed CyclodehydrationADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Kyoji Tsuchikama Abstract A directed cyclization-dehydration cascade of ,-aryloxy ketones and ,-arylamino ketones was efficiently catalyzed by a cationic iridium-BINAP complex, which afforded various types of 4-substituted benzofurans and indoles in high yields with complete regioselectivity. The newly developed protocol also enabled the enantioselective preparation of chiral 4-acetyloxindole using a chiral iridium catalyst. [source] Water-Soluble Group 8 and 9 Transition Metal Complexes Containing a Trihydrazinophosphaadamantane Ligand: Catalytic Applications in Isomerization of Allylic Alcohols and Cycloisomerization of (Z)-Enynols in Aqueous MediumADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 12-13 2006Abstract An optimized synthesis of the 2,4,10-trimethyl-1,2,4,5,7,10-hexaaza-3-phosphatricyclo[3.3.1.13,7]decane ligand (THPA) is described. It readily reacts with the dimers [{RuCl(,-Cl)(,6 -arene)}2] and [{MCl(,-Cl)(cod)}2] to yield the corresponding mononuclear complexes [RuCl2(THPA)(,6 -arene)] [arene=C6H6 (4a), p -cymene (4b), 1,3,5-C6H3Me3 (4c), C6Me6 (4d)] and [MCl(THPA)(cod)] [M=Rh (7a), Ir (7b)], respectively. Treatment of 4a and b with MeOTf affords the cationic derivatives [RuCl2(THPA-Me)(,6 -arene)][OTf] {arene=C6H6 (5a), p -cymene (5b); THPA-Me=1,2,4,10-tetramethyl-2,4,5,7,10-pentaaza-1-azonia-3-phosphatricyclo[3.3.1.13,7]decane}. The arene-ruthenium(II) complexes 4a,d and 5a and b are efficient catalysts for the redox isomerization of allylic alcohols into carbonyl compounds in both THF and aqueous media. The catalytic systems can be recycled by a simple extraction process and used in up to 4 consecutive runs. All the water-soluble complexes prepared in this work are able to promote the cycloisomerization of (Z)-enynols to afford furans in water, the best performance being obtained with the iridium catalyst 7b. Furthermore, 7b has shown an excellent recyclability (10 runs). This study represents the first example of iridium-catalyzed cycloisomerization of (Z)-enynols. [source] Highly Selective Iridium-Catalyzed Asymmetric Hydrogenation of Trifluoromethyl Olefins: A New Route to Trifluoromethyl- Bearing StereocentersADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009Mattias Engman Abstract Fluorine-containing compounds are useful in many applications ranging from pharmaceuticals to ferroelectric crystals. We have developed a new, highly enantioselective synthetic route to trifluoromethyl-bearing stereocenters in up to 96% ee via asymmetric hydrogenation using N,P-ligated iridium catalysts. We also hydrogenated an isomeric mixture of olefins; this reaction gave the hydrogenation product highly enantioselectively (87% ee), and only the E isomer was present after the reaction had reached 56% conversion. [source] | ||||||||||