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Cationic Iridium (cationic + iridium)
Terms modified by Cationic Iridium Selected AbstractsReduction of Alkyl Halides by Triethylsilane Based on a Cationic Iridium Bis(phosphinite) Pincer Catalyst: Scope, Selectivity and MechanismADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Jian Yang Abstract A highly efficient procedure for the reduction of a broad range of alkyl halides by triethylsilane based on a cationic iridium bis(phosphinite) pincer catalyst has been discovered and developed. This reduction chemistry is chemoselective and has unique selectivities compared with conventional radical-based processes and the aluminum trichloride/triethylsilane (AlCl3/Et3SiH) and triphenylmethyl tetrakis[pentafluorophenyl]borate/triethylsilane {[Ph3C] [B(C6F5)4]/Et3SiH} systems. Reductions use three equivalents of triethylsilane relative to the halide and can be carried out with very low catalyst loadings and in a solvent-free manner, which may provide an environmentally attractive and safe alternative to many currently practiced methods for reduction of alkyl halides. Mechanistic studies reveal a unique catalytic cycle. The cationic iridium hydride 2,6-bis[di-(tert -butyl)phosphinyloxy)phenyl(hydrido)iridium, (POCOP)IrH+ {POCOP= 2,6-[OP(t- Bu)2]2C6H3} binds and activates the silane. This complex serves as a potent silylating reagent to generate silyl halonium ions, Et3SiXR+, which are reduced by the neutral iridium dihydride to yield alkane product and regenerate the cationic (POCOP)IrH+, thus closing the catalytic cycle. All key intermediates have been identified by in situ NMR monitoring and kinetic studies have been completed. An application of this reduction system to the catalytic hydrodehalogenation of a metal chloride complex is also described. [source] ChemInform Abstract: Reduction of Alkyl Halides by Triethylsilane Based on a Cationic Iridium Bis(phosphinite) Pincer Catalyst: Scope, Selectivity and Mechanism.CHEMINFORM, Issue 23 2009Jian Yang 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 of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Highly Efficient and Enantioselective Iridium-Catalyzed Asymmetric Hydrogenation of N -AryliminesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Wei Li Abstract A catalytic method employing the cationic iridium-(Sc,Rp)-DuanPhos [(1R,1,R,2S,2,S)-2,2,-di- tert -butyl-2,2,,3,3, -tetrahydro-1H,1,H -1,1,-biisophosphindole] complex and BARF {tetrakis[3,5-bis(trifluoromethyl)phenyl]borate} counterion effectively catalyzes the enantioselective hydrogenation of acyclic N -arylimines with high turnover numbers (up to 10,000 TON) and excellent enantioselectivities (up to 98% ee), achieving the practical synthesis of chiral secondary amines. [source] Reduction of Alkyl Halides by Triethylsilane Based on a Cationic Iridium Bis(phosphinite) Pincer Catalyst: Scope, Selectivity and MechanismADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Jian Yang Abstract A highly efficient procedure for the reduction of a broad range of alkyl halides by triethylsilane based on a cationic iridium bis(phosphinite) pincer catalyst has been discovered and developed. This reduction chemistry is chemoselective and has unique selectivities compared with conventional radical-based processes and the aluminum trichloride/triethylsilane (AlCl3/Et3SiH) and triphenylmethyl tetrakis[pentafluorophenyl]borate/triethylsilane {[Ph3C] [B(C6F5)4]/Et3SiH} systems. Reductions use three equivalents of triethylsilane relative to the halide and can be carried out with very low catalyst loadings and in a solvent-free manner, which may provide an environmentally attractive and safe alternative to many currently practiced methods for reduction of alkyl halides. Mechanistic studies reveal a unique catalytic cycle. The cationic iridium hydride 2,6-bis[di-(tert -butyl)phosphinyloxy)phenyl(hydrido)iridium, (POCOP)IrH+ {POCOP= 2,6-[OP(t- Bu)2]2C6H3} binds and activates the silane. This complex serves as a potent silylating reagent to generate silyl halonium ions, Et3SiXR+, which are reduced by the neutral iridium dihydride to yield alkane product and regenerate the cationic (POCOP)IrH+, thus closing the catalytic cycle. All key intermediates have been identified by in situ NMR monitoring and kinetic studies have been completed. An application of this reduction system to the catalytic hydrodehalogenation of a metal chloride complex is also described. [source] | ||||||||||