Direct Asymmetric Hydrogenation and Dynamic Kinetic Resolution of Aryl Ketones Catalyzed by an Iridium‐NHC Exhibiting High Enantio‐ and Diastereoselectivity

Abstract

A chiral iridium carbene‐oxazoline catalyst is reported that is able to directly and efficiently hydrogenate a wide variety of ketones in excellent yields and good enantioselectivity (up to 93 % ee). Moreover, when using racemic α‐substituted ketones, excellent diastereoselectivities were obtained (dr 99:1) by dynamic kinetic resolution of the in situ formed enolate. Overall, the herein described hydrogenation occurs under ambient conditions using low hydrogen pressures, providing a direct and atom efficient method towards chiral secondary alcohols.

Palladium, iridium, and rhodium complexes bearing chiral N‐heterocyclic carbene ligands applied in asymmetric catalysis

“…Ayya Swamy et al recently reported Ir I complexes of type 168 possessing chiral oxazoline‐based NHC donor ligands (Scheme 24). [ 149 ] These complexes have been tested for the hydrogenation of a wide range of ketones, leading to the formation of chiral alcohols in excellent yields with good asymmetric induction (up to 93% ee). Furthermore, these complexes showed excellent diastereoselectivities ( dr 99:1) for racemic α‐substituted ketones via the dynamic kinetic resolution of the in situ generated enolate.…”

Enantioselective Hydroboration of Styrenes with Markovnikov Selectivity Catalyzed by a Rhodium(I)-NHC Complex

“…Salt metathesis of the in situ-formed silver carbenes with chloro-(1,5-cyclooctadiene)rhodium(I) dimer [RhCl(COD)] 2 in the presence of sodium tetrakis [3,5-bis(trifluoromethyl)phenyl]borate (NaBAr 4 F ) afforded the cationic rhodium complexes 5a−5e in good yields. The resulting metal complexes were characterized by 1 H, 13 C, 11 B, 19 F, and 2D-NMR spectroscopy as well as with high-resolution mass spectrometry (HRMS; see Supporting Information for more details). Unfortunately, despite multiple attempts, crystals amenable for X-ray diffraction could not be obtained.…”

“…Positive electrospray ionization time-of-flight mass spectrometry (TOF MS ES+) and high-resolution mass spectrometry (HRMS) were recorded on a Waters QTOFMS Xevo G2 spectrometer in the positive ion mode, and positive Atmospheric Pressure Chemical Ionization (TOF MS APCI+) was recorded on a Bruker maXis impact solid probe. The 1 H, 13 C, 11 B, 19 F, and 31 P NMR spectra were recorded on Bruker AVANCE III 400, and 600 MHz NMR spectrometers at room temperature unless mentioned otherwise. All chemical shifts (δ) are reported in ppm and coupling constants (J) are in Hz.…”

“…Recently, we reported chiral rhodium and iridium complexes based on a imidazo­[1,5- a ]­pyridine-oxazoline platform inspired by the design principles developed by Burgess et al, Glorius et al., and Lassaletta et al These complexes were used for the enantioselective hydrosilylation, and hydrogenation of ketones with moderate to good enantioselectivity . In order to improve the overall enantioselective induction in our previously reported imidazo­[1,5- a ]­pyridine-oxazoline platforms, we sought to introduce a second chiral substituent on the imidazo­[1,5- a ]­pyridine backbone, inspired by the chiral induction of the bulky 1-(naphthalen-1-yl)­ethyl substituent in Hermann’s Rhodium and Glorius’s ruthenium monodendate NHC catalysts …”

One‐Pot Construction of Fluorinated Chiral Alcohols via Sequential Substitution/Asymmetric Transfer Hydrogenation of α‐Bromoarylketones and Fluoroalcohols

“…Consequently, the development of efficient methods for the synthesis of α-functionalized chiral alcohols has attracted more and more attention. Among which, the most atom-economical method is asymmetric reduction of α-functionalized ketones via biocatalysis [1] or chemocatalysis catalyzed by Ru/Rh/IrÀ TsDPEN, [2] CBS-oxazaborolidine, [3] Al/3,3'-diphenyl-2,2'-bi-1-naphthol (VANOL), [4] Rh/P-chiral bis(phospholane) (DuanPhos), [5] Ru/biaryl tertiary diphosphine (SunPhos), [6] Ir/ferrorencebased amino-phosphinealcohol(f-Amphol), [7] Ru/2,2'-bis(diphenylphosphino)-1,1'-biphenyl (BIPHEP), [8] Ir/carbene, [9] Ru/2,2'-bis-(diphenylphos-phino)-1,1'-binaphthyl (BINAP), [10] spiroborate ester, [11] and chiral sulfonamide (Scheme 1a). [12] Alternatively, the α-functionalized chiral alcohols could also be prepared from α-bromo chiral alcohols with diversified nucleophiles.…”