Application of Crystallization-Induced Asymmetric Transformation to a General, Scalable Method for the Resolution of 2,8-Disubstituted Tröger’s Base Derivatives

Catalytic Asymmetric Synthesis of Tröger's Base Analogues with Nitrogen Stereocenter

Nitrogen stereocenters are common chiral units in natural products, pharmaceuticals, and chiral catalysts. However, their research has lagged largely behind, compared with carbon stereocenters and other heteroatom stereocenters. Herein, we report an efficient method for the catalytic asymmetric synthesis of Tröger's base analogues with nitrogen stereocenters via palladium catalysis and home-developed GF-Phos. It allows rapid construction of a new rigid cleft-like structure with both a C- and a N-stereogenic center in high efficiency and selectivity. A variety of applications as a chiral organocatalyst and metallic catalyst precursors were demonstrated. Furthermore, DFT calculations suggest that the NH···O hydrogen bonding and weak interaction between the substrate and ligand are crucial for the excellent enantioselectivity control.

A nitrogen-based chiral catenane for enantioenriching photocatalytic aerobic oxidation

Tröger's base's chirality merges catenanes’ photosensitizing characteristics to introduce the first nitrogen-based chiral hetero[2]catenane that proceeds enantioenriching photocatalytic aerobic oxidations.

Resolution of Thiele’s acid

Thiele’s acid has been resolved for the first time by diastereomeric salt formation with brucine. Determination of absolute stereochemistry was accomplished by X-ray crystallography of the corresponding diester. We anticipate that access to optically resolved Thiele’s acid will stimulate its use in a diverse range of applications requiring chiral molecular clefts.

Hünlich base derivatives as photo-responsive Λ-shaped hinges

The azo derivatives of the Hünlich base are introduced as a set of molecular switches with unique shapes and properties.

Highly diastereoselective crystallization-induced asymmetric transformation of 1,3-disubstituted-tetrahydro-β-carbolines in water

A green and highly stereoselective method for the synthesis of cis or trans-1,3-disubstituted-tetrahydro-β-carbolines has been developed using water as the solvent.

Accessing N-Stereogenicity through a Double Aza-Michael Reaction: Mechanistic Insights

Further development of the chemistry and applications of chiral compounds that possess configurationally stable stereogenic nitrogen atoms is hampered by the lack of efficient strategies to access such compounds in an enantiomerically pure form. Esters of propiolic acid and chiral alcohols were evaluated as cheap and readily available Michael acceptors in a diastereoselective synthesis of N-stereogenic compounds by means of a double aza-Michael conjugate addition. Diastereomeric ratios of up to 74:26 and high yields were achieved with (-)-menthyl propiolate as a substrate. Furthermore, a detailed mechanistic investigation was undertaken to shed some light on the course of this domino transformation. Kinetic studies revealed that the protic-solvent additive acts as a Brønsted acid and activates the ester toward the initial attack of the tetrahydrodiazocine partner. Conversely, acidic conditions proved unfavorable during the final cyclization step that provides the product.

Highly efficient and practical resolution of 2,3:6,7-dibenzobicyclo[3.3.1]nona-2,6-diene-4,8-dione and stereoselective synthesis of its chiral diamine derivatives

The rigid V-shaped molecule (±)-4 could be efficiently resolved by commercially available BINOL in high enantiomeric excesses.