The increasing demand to produce enantiomerically pure pharmaceuticals, agrochemicals, flavors, and other fine chemicals has advanced the field of asymmetric catalytic technologies.1,2 Among all asymmetric catalytic methods, asymmetric hydrogenation utilizing molecular hydrogen to reduce prochiral olefins, ketones, and imines, have become one of the most efficient methods for constructing chiral compounds.3 The development of homogeneous asymmetric hydrogenation was initiated by Knowles4a and Horner4b in the late 1960s, after the discovery of Wilkinson’s homogeneous hydrogenation catalyst [RhCl(PPh3)3]. By replacing triphenylphosphine of the Wilkinson’s catalystwithresolvedchiralmonophosphines,6Knowles and Horner reported the earliest examples of enantioselective hydrogenation, albeit with poor enantioselectivity. Further exploration by Knowles with an improved monophosphine CAMP provided 88% ee in hydrogenation of dehydroamino acids.7 Later, two breakthroughs were made in asymmetric hydrogenation by Kagan and Knowles, respectively. Kagan reported the first bisphosphine ligand, DIOP, for Rhcatalyzed asymmetric hydrogenation.8 The successful application of DIOP resulted in several significant directions for ligand design in asymmetric hydrogenation. Chelating bisphosphorus ligands could lead to superior enantioselectivity compared to monodentate phosphines. Additionally, P-chiral phosphorus ligands were not necessary for achieving high enantioselectivity, and ligands with backbone chirality could also provide excellent ee’s in asymmetric hydrogenation. Furthermore, C2 symmetry was an important structural feature for developing new efficient chiral ligands. Kagan’s seminal work immediately led to the rapid development of chiral bisphosphorus ligands. Knowles made his significant discovery of a C2-symmetric chelating bisphosphine ligand, DIPAMP.9 Due to its high catalytic efficiency in Rh-catalyzed asymmetric hydrogenation of dehydroamino acids, DIPAMP was quickly employed in the industrial production of L-DOPA.10 The success of practical synthesis of L-DOPA via asymmetric hydrogenation constituted a milestone work and for this work Knowles was awarded the Nobel Prize in 2001.3k This work has enlightened chemists to realize * Corresponding author. 3029 Chem. Rev. 2003, 103, 3029−3069

New Chiral Phosphorus Ligands for Enantioselective Hydrogenation

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

C–H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material sciences, crop protection, drug discovery, and pharmaceutical industries, among others. Despite major advances, the vast majority of these C–H functionalizations required precious 4d or 5d transition metal catalysts. Given the cost-effective and sustainable nature of earth-abundant first row transition metals, the development of less toxic, inexpensive 3d metal catalysts for C–H activation has gained considerable recent momentum as a significantly more environmentally-benign and economically-attractive alternative. Herein, we provide a comprehensive overview on first row transition metal catalysts for C–H activation until summer 2018.

3d Transition Metals for C-H Activation.

Complete Field Guide to Asymmetric BINOL-Phosphate Derived Brønsted Acid and Metal Catalysis: History and Classification by Mode of Activation; Brønsted Acidity, Hydrogen Bonding, Ion Pairing, and Metal Phosphates

Green solvents for sustainable organic synthesis: state of the art

Catalytic asymmetric C-C bond-forming reactions using organometallic reagents are among the most important of organic transformations. Frequently, these transformations are key steps in the synthesis of complex biologically active molecules. The conjugate addition (CA) and allylic alkylation (AA) with organometallic compounds are especially versatile in asymmetric C-C bond-forming reactions. These transformations are complementary to the catalytic asymmetric allylic alkylation and the Michael addition, both based on soft carbon nucleophiles (Scheme 1A). For both CA and AA, the organic moiety of the organometallic reagent reacts with the sp carbon of an electron-deficient substrate, converting it to an sp carbon (Scheme 1B). In the case of CA, subsequent quenching of the enolate leads to the final product, whereas for the related AA an appropriate leaving group is expelled to form the chiral product. The organometallic compounds used most frequently for these transformations are organozinc, Grignard, organoaluminium, organolithium and cuprate reagents. Over the last three decades considerable effort has been directed toward the development of efficient catalytic systems for the asymmetric CA and AA reactions using organometallic reagents. Complexes derived from Cu salts and chiral ligands have provided the broadest scope in the catalyzed enantioselective CA and AA of organometallic reagents. Organozinc reagents have been the most successful of the organometallic reagents in this respect. Major contributions and progress in the field of asymmetric CA and AA based on organozinc reagents have been summarized in several reviews. Organomagnesium compounds were among the first organometallic compounds to be applied to synthetic organic chemistry and the use of Grignard reagents in Cu-catalyzed CA was first reported in 1941 by Kharash and Tawney. Achieving chemo-, regioand stereocontrol in both asymmetric conjugate addition (ACA) and asymmetric allylic alkylation (AAA), however, has proven to be challenging and has restricted the application of these transformations, in particular, to total synthesis. Typical selectivity issues pertain to 1,2versus 1,4-addition (Scheme 2A) and SN2versus SN2′-substitution (Scheme 2B). The challenge faced in the development of stereoselective C-C bond-forming reactions is apparent when one considers that, despite three decades of intensive research in this area, only recently has efficient Cu-catalyzed enantioselective CA of Grignard reagents been achieved. The earlier discovery of the highly enantioselective Cu-catalyzed CA of dialkylzinc reagents allowed for replacement of Grignard reagents in this asymmetric C-C bond-forming reaction. Dialkylzinc reagents offer distinct advantages over Grignard reagents in their low reactivity in noncatalyzed reactions and their high tolerance to functional groups both on the substrate and on the organozinc reagent itself. Nevertheless, there are several advantages to the use of common mono-alkylMg halide reagents, most importantly their widespread availability and the ability to transfer all of the alkyl groups of the organometallic compound. The synthetic potential of these asymmetric transformations has driven intensive research in this area, and over the past few years major breakthroughs have been realized in the enantioselective CA and AA of Grignard reagents. * Author for correspondence. E-mail: B.L.Feringa@rug.nl Chem. Rev. 2008, 108, 2824–2852 2824

Catalytic asymmetric conjugate addition and allylic alkylation with Grignard reagents.

In this critical review, the progress in catalytic asymmetric synthesis of β-amino acids is discussed, covering the literature since 2002. The review treats transition metal catalysis, organocatalysis and biocatalysis and covers the most important synthetic methods, such as hydrogenation, the Mannich reaction and conjugate additions (160 references).

Recent advances in the catalytic asymmetric synthesis of β-amino acids

The homogeneous enantioselective hydrogenation of functionalized prochiral olefins is one of the most frequently studied and most efficient transition metal-catalyzed reactions. In the first reports using chiral Wilkinson type catalysts, low enantiomeric excesses (ee’s) were obtained using monodentate phosphines as ligands. All attempts to develop monodentate ligands which would afford high ee’s in this reaction met with limited success, the best result being reached with CAMP, already published in 1972, giving ee’s up to 90% in the hydrogenation of dehydroamino acids. Although new monodentate phosphorus ligands play a significant role in other transition metal-catalyzed reactions, highly enantioselective hydrogenations are exclusively based on bidentate phosphorus ligands. Starting with Kagan’s diop a large number of bidentate ligands with excellent selectivities was designed. Among the most successful are DIPAMP, which gives superior results compared to its monodentate analogue PAMP, the frequently used BINAP ligand, the ferrocenyl-based ligands and the DuPHOS, BPE, and FerroTANE ligands, the latter showing extremely high enantioselectivities and broad scope. To date, not only phosphines (phosphanes) are used but also bidentate aminophosphines, phosphites, phosphinites, phosphonites, and hybrid ligands such as phosphine-phosphite, aminophosphine-phosphinite, and phosphine-phosphonite,

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Highly Enantioselective Rhodium-Catalyzed Hydrogenation with Monodentate Ligands

A comprehensive overview of recent literature from 2003 concerning advances in enantioselective copper catalysed 1,4-addition of organometallic reagents to alpha,beta-unsaturated compounds is given in this critical review. About 200 ligands and catalysts are presented, with a focus on stereoselectivities, catalyst loading, ligand structure and substrate scope. A major part is devoted to trapping and tandem reactions and a variety of recent synthetic applications are used to illustrate the practicality and current state of the art of 1,4-addition of organometallic reagents. Finally several mechanistic studies are discussed (162 references).

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Recent advances in enantioselective copper-catalyzed 1,4-addition.

Monodentate phosphoramidites are excellent ligands for Rh-catalyzed asymmetric hydrogenations of substituted olefins Enantioselectivities between 95 and 99% were obtained in the asymmetric hydrogenation of protected α- and β-dehydroamino acids and esters, itaconic acid and esters, aromatic enamides, aromatic enol esters, aromatic and aliphatic enol carbamates, and α-substituted cinnamic acids An iridium catalyst Ir(L*)(COD)Cl was developed that contains only a single bulky phosphoramidite based on 3,3′-disubstituted BINOL or bisphenol as a chiral ligand With this catalyst, acetylated dehydroamino acid esters could be hydrogenated with very good enantioselectivity Most reactions have turnover frequencies of 250–1600 h −1, depending upon the hydrogen pressure The enantioselectivity is unaffected by the pressure over a wide range Because of their modularity and easy synthesis, parallel ligand synthesis is possible Results obtained with these library ligands deviate only slightly from those obtained wi

Adriaan J. Minnaard

Papers

Catalytic asymmetric conjugate addition and allylic alkylation with Grignard reagents.

Recent advances in the catalytic asymmetric synthesis of β-amino acids

Highly Enantioselective Rhodium-Catalyzed Hydrogenation with Monodentate Ligands

Recent advances in enantioselective copper-catalyzed 1,4-addition.

Asymmetric hydrogenation using monodentate phosphoramidite ligands.