Catalysis, kinetics and mechanisms of organo-iridium enantioselective hydrogenation-reduction

Abstract

The synthesis of chiral molecules is of great importance to the pharmaceutical, agrochemical, flavour and fragrance industries.

Iridium‐Catalyzed Acid‐Assisted Hydrogenation of Oximes to Hydroxylamines

“…Next, the uncoordinated 1‐H + is reduced by separately receiving a hydride from [Ir‐H] and subsequently a proton from MsOH. This outer‐sphere hydrogenation mechanism is termed ionic hydrogenation [22f–i] . It has as well been proposed for related catalytic imine hydrogenations [14d, 22j,k] .…”

Carboxamide substituted tetramethylcyclopentadiene – synthesis, characterisation and its iridium(iii) complex catalysed reduction of imines

“…7 We followed this exchange (Fig. 4) by 1 The difference of only 0.8 pK a units shows poor transmission of the expected electronic effect of CONMe 2 group. Our DFT calculations (see ESI-S8 ‡) of the neutral Cp*CONMe 2 predicts a dihedral angle between the cyclopentadiene ring and carbonyl group of about 90°, which in the carbanion is about 30°.…”

“…The cooled reaction mixture was poured into ice-water and extracted with EtOAc (2 × 200 mL). The aqueous layer was basified with solid NaOH pellets to pH 11 and this was extracted with EtOAc (2 × 100 mL), dried with Na 2 SO 4 and dried in vacuo to afford 1-methyl-3,4-dihydroisoquinoline as a white solid, (12.5 g, 90%): 1…”

“…one via first order and one zero-order kinetics. 1 In such cases the enantiomeric excess (ee) changes as the reaction proceeds because the rate of formation of the enantiomeric product following first-order kinetics decreases as the reac-tion proceeds whereas that showing a zero-order profile is independent of the concentration of the reactant. 2 The asymmetric transfer hydrogenation (ATH) of imines to amines occupies a cluster of reactions which utilise simple hydrogen donors such as formic acid and iso-propanol in conjunction with a base, offering operational simplicity to reduce prochiral substrates into their enantiomeric components in a selective fashion, achieving high yields with high ee's.…”

“…The pentamethylcyclopentadienyl anion (Cp*) engages the metal centre via strong 6π-electron binding in a η 5 fashion, with permethylation increasing basicity and electron density as well as providing steric protection of the metal centre. 1 An electron withdrawing group on the Cp* carbanionic ligand is anticipated to decrease its basicity and increase positive charge density on Ir making the process of hydride transfer from Ir-H harder (slowing down the k 2 value) (Scheme 1). Detailed in this report are the investigations of this manipulation of attaching an electron withdrawing tertiary amide group to Cp*.…”