Chiral iridium diphosphine catalysts

Ru Availability of a wide range of chiral dia mines and diphosphines simplifies com binatorial style searches for the most suitable catalyst for a given substrate. In general, less enantioselective than iridium based catalysts. 

Takeuchi and coworkers reported an iridium-catalyzed cycloaddition of a,o -diynes and nitriles to give pyridines in 2012 [57]. With [Ir (cod)Cl]2/DPPF or BINAP as the catalytic system, pyridines were formed effectively (Scheme 3.24). A wide range of nitriles (aliphatic and aromatic nitriles) can be applied and reacted smoothly with Q ,a -diynes to give the pyridines. In the case of unsymmetrical diyne bearing two different internal alkyne moieties, high regioselectivity can be achieved which can be explained by the different reactivities of the a-position in iridacyclopentadiene. Terpyridine and quinquepyridine were prepared as well. [Ir(cod)Cl]2/chiral diphosphine catalyst can be applied to enantioselective synthesis. Kinetic resolution of the racemic... 

Nowadays enantioselective synthesis of the herbicide (5)-metolachlor (Dual Magnum) is, to our knowledge, one of the most successful commercial applications of asymmetric C=N bond hydrogenation. Developed by Blaser and Spindler as a key step in the technical synthesis of (5)-metolachlor, the enantioselective hydrogenation of an imine intermediate 193 proceeds in the presence of an iridium ferrocenyl-diphosphine catalyst bearing a Solvias Josiphos-type chiral ligand (/ )-Xyliphos to give... 

Iridium The intermolecular hydroamination of unactivated C=C bonds in ct-olefins (RCH=CH2) and bicycloalkenes (norbornene and norbornadiene) with arylamides (ArCONH2) and sulfonamides has been attained upon catalysis by chiral iridium complexes (PP)IrHCl(NHCOAr)(NH2COAr) [PP = chiral bidentate diphosphine]. Mechanistic studies identified the product of N-H bond oxidative addition and coordination of the amide as the resting state of the catalyst. Rapid, reversible dissociation of the amide precedes reaction with the alkene, but an intramolecular, kinetically significant rearrangement of the species occurs before the reaction with alkene. ... 

The reaction of 3,4-dihydroisoquinoline A-oxide (74) and methacrylonitrile in the presence of cationic half-sandwich rhodium and iridium complexes containing a chiral diphosphine ligand was analyzed. The cycloadditions occurred with excellent regio- and diastereoselectivity and low-to-moderate enantioselectivity. Analysis of the catalytic system showed the formation of two epimeric complexes 75 containing the dipolarophile methacrylonitrile. The reaction of one of the isolated diastereopure complexes 75 with 74 afforded cycloadduct 76 with high enantioselectivity. A recycling procedure was developed in order to increase the adduct/catalyst ratio <07CEJ9746>. 

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