Asymmetric Hydrosilylation of Ketones Catalyzed by Zinc Acetate with Hindered Pybox Ligands

Electrochemical Radical Reactions of Enol Acetates and Free Alcohols Directly Access to α-Alkoxylated Carbonyl Compounds

The efficient intermolecular alkoxylation reactions of various enol acetates and different alcohols are developed in the electrochemical process for the first time. Enol acetates derived from either aromatic, alkyl, or alicyclic ketones, and abundant free alcohols directly used in this synthetic strategy, make this transformation very valuable in synthesis and application in the future.

Further Developments and Applications of Oxazoline-Containing Ligands in Asymmetric Catalysis

The chiral oxazoline motif is present in many ligands that have been extensively applied in a series of important metal-catalyzed enantioselective reactions. This Review aims to provide a comprehensive overview of the most significant applications of oxazoline-containing ligands reported in the literature starting from 2009 until the end of 2018. The ligands are classified not by the reaction to which their metal complexes have been applied but by the nature of the denticity, chirality, and donor atoms involved. As a result, the continued development of ligand architectural design from mono(oxazolines), to bis(oxazolines), to tris(oxazolines) and tetra(oxazolines) and variations thereof can be more easily monitored by the reader. In addition, the key transition states of selected asymmetric transformations will be given to illustrate the features that give rise to high levels of asymmetric induction. As a further aid to the reader, we summarize the majority of schemes with representative examples that highlight the variation in % yields and % ees for carefully selected substrates. This Review should be of particular interest to the experts in the field but also serve as a useful starting point to new researchers in this area. It is hoped that this Review will stimulate both the development/design of new ligands and their applications in novel metal-catalyzed asymmetric transformations.

Chiroptical methods in a wide wavelength range for obtaining Ln3+ complexes with circularly polarized luminescence of practical interest

We studied enantiopure chiral trivalent lanthanide (Ln3+ = La3+, Sm3+, Eu3+, Gd3+, Tm3+, and Yb3+) complexes with two fluorinated achiral tris(β-diketonate) ligands (HFA = hexafluoroacetylacetonate and TTA = 2-thenoyltrifluoroacetonate), incorporating a chiral bis(oxazolinyl)pyridine (PyBox) unit as a neutral ancillary ligand, by the combined use of optical and chiroptical methods, ranging from UV to IR both in absorption and circular dichroism (CD), and including circularly polarized luminescence (CPL). Ultimately, all the spectroscopic information is integrated into a total and a chiroptical super-spectrum, which allows one to characterize a multidimensional chemical space, spanned by the different Ln3+ ions, the acidity and steric demand of the diketone and the chirality of the PyBox ligand. In all cases, the Ln3+ ions endow the systems with peculiar chiroptical properties, either allied to f-f transitions or induced by the metal onto the ligand. In more detail, we found that Sm3+ complexes display interesting CPL features, which partly superimpose and partly integrate the more common Eu3+ properties. Especially, in the context of security tags, the pair Sm/Eu may be a winning choice for chiroptical barcoding.

Carbonyl and ester C–O bond hydrosilylation using κ4-diimine nickel catalysts

(^Ph2PPrDI)Ni chemoselectively catalyzes α-allyl ester C–O bond hydrosilylation to prepare silyl esters with turnover frequencies of up to 990 h⁻¹.

Highly Enantioselective Hydrosilylation of Ketones Catalyzed by a Chiral Oxazaborolidinium Ion

A highly enantioselective hydrosilylation of ketones was developed for the synthesis of a variety of chiral secondary alcohols. In the presence of a chiral oxazaborolidinium ion (COBI) catalyst, the reaction proceeded with good yields (up to 99%) with excellent enantioselectivities (up to 99% ee).

Iron-Catalyzed Asymmetric Nitro-Mannich Reaction

The first enantioselective addition of nitroalkanes to imines (nitro-Mannich reaction), mediated by an iron(II) catalyst assembled by a hindered hydroxyethyl-pybox ligand, is described. This valuable carbon-carbon bond-forming reaction proceeds smoothly at room temperature to afford enantioenriched β-nitro amines in good yields and high enantioselectivity, up to 98% with unprecedentedly low iron catalyst loading (5 mol %).

Manganese-Catalyzed Asymmetric Hydrosilylation of Aryl Ketones

We disclose the synthesis of a series of manganese complexes of chiral iminopyridine oxazoline ligands and their application in the first manganese-catalyzed asymmetric ketone hydrosilylations. The most sterically hindered manganese catalyst bearing two CH(Ph)₂ groups at the 2,6-ortho positions of the imino aryl ring and a tBu group on the oxazoline ring furnishes the secondary alcohols in high enantioselectivities and yields.

Pure phosphotriesters as versatile ligands in transition metal catalysis: efficient hydrosilylation of ketones and diethylzinc addition to aldehydes

The phosphate fate: will proving the versatility of phosphate ligands in catalysis make them finally attractive?

Fine tuning of molecular and supramolecular properties of simple trianglimines – the role of the functional group

Readily available chiral, triangular poly-azamacrocycles can act as receptors, low molecular weight supergelators and ligands in asymmetric synthesis.

Enantioselective Hydrosilylation of Imines Catalyzed by Chiral Zinc Acetate Complexes

A series of zinc acetate complexes with optically pure diphenylethanediamine (DPEDA)-derived ligands have been employed as enantioselective catalyst for the hydrosilylation of various imines. High control of stereoselectivity (up to 97% ee) and excellent yields (up to 96%) were gained for a broad range of N-phosphinoylimines by using (R,R)-N,N'-dibenzyl-1,2-diphenylethane-1,2-diamine. This is the first successful application of an air-stable and environmentally friendly chiral Zn(OAc)2 complex instead of the previously used harmful diethylzinc in the asymmetric reduction of the C═N double bond.

Iron-catalyzed asymmetric hydrosilylation of ketones

Iron complexes of chiral iminopyridine-oxazoline (IPO) ligands effectively catalyze asymmetric hydrosilylation of aryl ketones.