Bulky Achiral Triarylphosphines Mimic BINAP in Ru(II)- Catalyzed Asymmetric Hydrogenation of Ketones

Cinchona-Alkaloid-Derived NN Ligands and Achiral Phosphines for Iridium-Catalyzed Asymmetric Hydrogenation of Heteroaromatic and α-Chloroheteroaryl Ketones

A concise synthesis of cinchona-alkaloid-derived NN ligands bearing alkyl substituents on chiral nitrogen atoms was described. Iridium catalysts containing new chiral NN ligands and achiral phosphines were effective for the asymmetric hydrogenation of heteroaromatic ketones, which afforded corresponding alcohols in up to 99.9% ee. The same protocol was applicable to the asymmetric hydrogenation of α-chloroheteroaryl ketones. Most importantly, the gram-scale asymmetric hydrogenation of 2-acetylthiophene and 2-acetylfuran proceeded smoothly even under 1 MPa of H2.

The crystal structure of trans-dichlorido-(ethylenediamine-κ 2 N,N′)-bis(triphenylphosphine-κ 1 P)ruthenium(II), C38H38Cl2N2P2Ru

C38H38Cl2N2P2Ru, monoclinic, P21/c (no. 14), a = 10.8827(3) Å, b = 30.6226(7) Å, c = 20.2089(4) Å, β = 93.8560(10)°, V = 6719.5(3) Å3, Z = 8, Rgt (F) = 0.0306, wRref (F 2) = 0.0636, T = 173(2) K.

Automation and Microfluidics for the Efficient, Fast, and Focused Reaction Development of Asymmetric Hydrogenation Catalysis

Automation and microfluidic tools potentially enable efficient, fast, and focused reaction development of complex chemistries, while minimizing resource- and material consumption. The introduction of automation-assisted workflows will contribute to the more sustainable development and scale-up of new and improved catalytic technologies. Herein, the application of automation and microfluidics to the development of a complex asymmetric hydrogenation reaction is described. Screening and optimization experiments were performed using an automated microfluidic platform, which enabled a drastic reduction in the material consumption compared to conventional laboratory practices. A suitable catalytic system was identified from a library of Ru^II -diamino precatalysts. In situ precatalyst activation was studied with ¹ H/³¹ P nuclear magnetic resonance (NMR), and the reaction was scaled up to multigram quantities in a batch autoclave. These reactions were monitored using an automated liquid-phase sampling system. Ultimately, in less than a week of total experimental time, multigram quantities of the target enantiopure alcohol product were provided by this automation-assisted approach.

Copper-Catalyzed Asymmetric Reductions of Aryl/Heteroaryl Ketones under Mild Aqueous Micellar Conditions

Enantioselective syntheses of nonracemic secondary alcohols have been achieved in an aqueous micellar medium via copper-catalyzed (Cu(OAc)₂·H₂O/(R)-3,4,5-MeO-MeO-BIPHEP) reduction of aryl/heteroaryl ketones. This methodology serves as a green protocol to access enantio-enriched alcohols under mild conditions (0-22 °C) using a base metal catalyst, together with an inexpensive, innocuous, and convenient stoichiometric hydride source (PMHS). The secondary alcohol products are formed in good to excellent yields with ee values greater than 90%.

A combined experimental and computational study to decipher complexity in the asymmetric hydrogenation of imines with Ru catalysts bearing atropisomerizable ligands

RuCl₂(P–OP)(N–N) complexes containing an atropisomerizable phosphine–phosphite and a chiral diamine are effective catalyst precursors for the asymmetric hydrogenation of N-aryl imines following an outer-sphere mechanism.

Two tris-(3,5-disubstituted phen-yl)phosphines and their isostructural PV oxides

The crystal structures of tris-(3,5-di-methyl-phen-yl)phosphine (C24H27P), (I), tris-(3,5-di-methyl-phen-yl)phosphine oxide (C24H27OP), (II), tris-(4-meth-oxy-3,5-di-methyl-phen-yl)phosphine (C27H33O3P), (III), and tris-(4-meth-oxy-3,5-di-methyl-phen-yl)phosphine oxide (C27H33O4P), (IV), are reported. The strucure of (III) has been described before [Romain et al. (2000 ▸). Organometallics, 19, 2047-2050], but it is rereported here on the basis of modern area-detector data and to facilitate comparison with the other structures reported here. Compounds (I) and (II) crystallize isostructurally in P21/c. Similarly, (III) and (IV) crystallize isostructurally in Pbca. The conformations of (I) and (II) in the solid state deviate strongly from helical, whereas those of (III) and (IV) are found to be closer to an ideal threefold rotational symmetry. The pyramidality indices, ∑(C-P-C), are 305.35 (16), 317.23 (15), 307.2 (4) and 318.67 (18)° for (I), (II), (III) and (IV), respectively. Each is found to be more pyramidal than Ph3P or Ph3PO. Hybrid DFT calculations incorporating terms for dispersion provide evidence that the causes of the increased pyramidality, despite the 3,5-dimethyl group substitution, include dispersion inter-actions. The calculated ∑(C-P-C) values are 304.8° for both (I) and (III) and 317.4° for both (II) and (IV), with no difference arising from the substitution at ring position 4.

Highly enantioselective Ir/f-amphox-catalyzed hydrogenation of ketoamides: efficient access to chiral hydroxy amides

Asymmetric synthesis of chiral hydroxy amides has been successfully accomplished by asymmetric hydrogenation of prochiral α-, β-, γ-, δ-keto amides catalyzed by Ir/f-amphox with up to >99% conversion and >99% ee.

Enantio- and diastereoselective synthesis of γ-amino alcohols

Two complementary catalytic diastereoselective methods for the synthesis of N-PMP-protected γ-amino alcohols from the corresponding ketones have been developed.

The N-H functional group in organometallic catalysis

The organometallic approach is one of the most active topics in catalysis. The application of NH functionality in organometallic catalysis has become an important and attractive concept in catalyst design. NH moieties in the modifiers of organometallic catalysts have been shown to have various beneficial functions in catalysis by molecular recognition through hydrogen bonding to give catalyst-substrate, ligand-ligand, ligand-catalyst, and catalyst-catalyst interactions. This Review summarizes recent progress in the development of the organometallic catalysts based on the concept of cooperative catalysis by focusing on the NH moiety.