3,3‘-Disubstituted BINAP Ligands: Synthesis, Resolution, and Applications in Asymmetric Hydrogenation

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.

Enantioselectivity Induced by Stereoselective Interlocking: A Novel Core Motif for Tropos Ligands

Well-defined supramolecular interactions are a powerful tool to control the stereochemistry of a catalytic reaction. In this paper, we report a novel core motif for fluxional 2,2'-biphenyl ligands carrying (S)-amino acid-derived interaction sites in 5,5'-position that cause spontaneous enrichment of the R_ax rotamer. The process is based on strong non-covalent interlocking between interaction sites, which causes diastereoselective formation of a supramolecular ligand dimer, in which the axial chirality of the two subunits is dictated by the stereochemical information in the amino acid residues. The detailed structure of the dimer was elucidated by NMR spectroscopy and single-crystal X-ray analysis. Three different phosphorus-based ligand types, namely a bisphosphine, a bisphosphinite and a phosphoramidite were synthesized and characterized. Whereas the first one was found to exist in a strongly weighted equilibrium, the two others each exhibited stereoconvergent behavior transforming into the diastereopure R_ax rotamer. Enriched ligands were used in rhodium-mediated asymmetric hydrogenation reactions of prochiral olefins in which very high enantioselectivities of up to 96:4 were achieved.

Various difunctionalizations of acrylamide: an efficient approach to synthesize oxindoles

In this review, we summarize the advancement and applications in the difunctionalization of acrylamide to synthesize oxindoles based on the mechanism.

Prediction of enantioselectivity in rhodium catalyzed hydrogenations

Using the Q2MM method, new molecular mechanics parameters were developed to perform initial screening of a chiral library to focus the experimental screening for the rhodium catalyzed hydrogenation of enamides. Computational predictions agree very well with experimental data.

Diastereospecific intramolecular Ullmann couplings: unique chiral auxiliary for the preparation of 3,3'-disubstituted MeO-BIPHEP derivatives

[reaction: see text] A chiral auxiliary is described that provides only one diastereomer during intramolecular Ullmann couplings. Treatment of five Ullmann coupling precursors with Cu powder in DMF at 115 degrees C provides 2,2',3,3',6,6'-hexasubstituted 1,1'-biphenyls as single diastereomers in yields ranging from 66% to 91%.

2,2′-Disubstituted F12binaphthyl derivatives: stannanes, boranes, and (R)-F12BINOL

2,2'-Distannyl derivatives of dodecafluorobinaphthalene are converted to a novel D2 symmetric borane dimer, which can be oxidized to (+)-F12BINOL; resolution using (S)-acetoxypropanoyl chloride affords enantiopure material.