Iridium Catalyst Cyclopropanation

Other chiral metal catalysts such as iridium, osmium, and rhenium catalysts have also been utilized for asymmetric cyclopropanation. In particular, iridium catalyst gave exceptional enantio- and diastereoselectivities. Chiral Ir(III) salen complexes, which contain a-coordinated aryl ligands, were found to catalyze the cyclopropanation of st3rrene derivatives with TDA. Higher yields (99%), higher diastereoselectivity t/c = 1 99), and enantioselectivity (99% ee) were observed when the reactions were conducted at lower temperature (—78°C) (98). For osmium, an Schiff-based complex of [Os(fBu-salch)(OH)Cl] (H2tBu-salch... 

The metal-catalysed hydrogenation of cyclopropane has been extensively studied. Although the reaction was first reported in 1907 [242], it was not until some 50 years later that the first kinetic studies were reported by Bond et al. [26,243—245] who used pumice-supported nickel, rhodium, palladium, iridium and platinum, by Hayes and Taylor [246] who used K20-promoted iron catalysts, and by Benson and Kwan [247] who used nickel on silica—alumina. From these studies, it was concluded that the behaviour of cyclopropane was intermediate between that of alkenes and alkanes. With iron and nickel catalysts, the initial rate law is... 

Experimental data have provided evidence for the involvment of quantum mechanical tunnelling in the coupled cobalt-carbon bond homolysis-substrate radical generation reaction catalysed by methylmalonyl-CoA mutase. ortho-Metallated dirhodium(II) complexes have been used as catalysts in the dia-stereoselective cyclopropanation of menthyl-a-diazo-P-keto ester and C-H insertion of ot-diazo ester. The iridium complexes [Ir(Me)2(L)(r -C5Me5)] (L = PMes, PPhs) have been found to catalyse the dehydrogenative coupling of dimethylphenylsilane in the presence of one-electron oxidants to yield Me2PhSiSiPhMe2. ... 

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