Highly Enantioselective Hydrogenation of α-Dehydroamino Esters and Itaconates with Triphosphorous Bidentate Ligands and the Unprecedented Solvent Effect Thereof

o-Hydroxyarylphosphanes: Strategies for Syntheses of Configurationally Stable, Electronically and Sterically Tunable Ambiphiles with Multiple Applications

o-Hydroxyarylphosphanes are fascinating compounds by their multiple-reactivity features, attributed to the ambident hard and soft Lewis- and also Brønstedt acid-base properties, wide tuning opportunities via backbone substituents with ±mesomeric and inductive, at P and in o-position to P and O also steric effects, and in addition, the configurational stability at three-valent phosphorus. Air sensitivity may be overcome by reversible protection with BH3 , but the easy oxidation to P(V)-compounds may also be used. Since the first reports on the title compounds ca. 50 years ago the multiple reactivity has led to versatile applications. This includes various P-E-O and P=C-O heterocycles, a multitude of O-substituted derivatives including acyl derivatives for traceless Staudinger couplings of biomolecules with labels or functional substituents, phosphane-phosphite ligands, which like the o-phosphanylphenols itself form a range of transition metal complexes and catalysts. Also main group metal complexes and (bi)arylphosphonium-organocatalysts are derived. Within this review the various strategies for the access of the starting materials are illuminated, including few hints to selected applications.

Application of Transition-Metal Catalysis, Biocatalysis, and Flow Chemistry as State-of-the-Art Technologies in the Synthesis of LCZ696

LCZ696 is a novel treatment for patients suffering from heart failure that combines the two active pharmaceutical ingredients sacubitril and valsartan in a single chemical compound. While valsartan is an established drug substance, a new manufacturing process suitable for large-scale commercial production had to be developed for sacubitril. The use of chemocatalysis, biocatalysis, and flow chemistry as state-of-the-art technologies allowed to efficiently build up the structure of sacubitril and achieve the defined performance targets.

Chiral phosphine-phosphoramidite ligands for highly enantioselective hydrogenation of N-arylimines

The asymmetric hydrogenation of N-arylimines with the chiral phosphine-phosphoramidite ligand, (Sc,Sa)-PEAPhos 2b, has been developed, in which high turnover numbers and excellent enantioselectivity were achieved.

Enhancement of stereoselectivities in asymmetric synthesis using fluorinated solvents, auxiliaries, and catalysts

In this review, the drastic changes using fluorinated solvents, additives, auxiliaries, and catalysts in catalytic asymmetric transformations are presented.

The influence of fluorine in asymmetric catalysis

All domains of chemistry are increasingly impacted by organofluorine molecules, often favorably. In asymmetric synthesis of fluorinated compounds, significant achievements are the result of extensive research efforts toward appropriate experimental conditions rather than of the rationalization of fluorine effects. Most of the time, the influence of fluorine is inspected retrospectively. When elaborating a synthetic plan, the question should not be only when and how to introduce fluorine but also how to use the effects of fluorine for a desirable result. The subtle effects of fluorine atom(s) on the course of asymmetric reactions are outlined in this tutorial review. We present some selected examples of asymmetric reactions that involve fluorinated components either as reactants, catalysts, solvents or additives, and a comparative study of the stereochemical outcomes with reactions carried out in the presence of non-fluorinated analogues.

Synthesis and characterization of privileged monodentate phosphoramidite ligands and chiral Brønsted acids derived from d-mannitol

The synthesis of several novel chiral phosphoramidite ligands (L1-L8) with C(2) symmetric, pseudo C(2) symmetric secondary amines and chiral Brønsted acids 1a,b has been achieved. These chiral auxiliaries were obtained from commercially available d-mannitol, and secondary amines in moderate to excellent yields. Excellent diastereoselectivites of ten chiral auxiliaries were obtained. The chiral phosphoramidite ligands and chiral Brønsted acids were fully characterized by spectroscopic methods.

Hybrid bidentate phosphorus ligands in asymmetric catalysis: privileged ligand approach vs. combinatorial strategies

In this perspective the development of chiral phosphorus ligands for asymmetric catalysis is discussed, with a special focus on hybrid bidentate phosphorus ligands, in particular phosphine-phosphoramidites. An attempt is made to compare privileged ligand and combinatorial approaches to ligand development--for which the class of phosphine-phosphoramidite ligands is well suited--highlighting differences, similarities and their complementary use.

Asymmetric hydrogenation of di and trisubstituted enol phosphinates with N,P-ligated iridium complexes

The iridium-catalyzed asymmetric hydrogenation of various di- and trisubstituted enol phosphinates has been studied. Excellent enantioselectivities (up to >99% ee) and full conversion were observed for a range of substrates with both aromatic and aliphatic side chains. Enol phosphinates are structural analogues of enol acetates, and the hydrogenated alkyl phosphinate products can easily be transformed into the corresponding alcohols with conservation of stereochemistry. We have also hydrogenated, in excellent ee, several purely alkyl-substituted enol phosphinates, producing chiral alcohols that are difficult to obtain highly enantioselectively from ketone hydrogenations.