Highly Enantioselective Transfer Hydrogenation of Quinolines Catalyzed by Gold Phosphates: Achiral Ligand Tuning and Chiral-Anion Control of Stereoselectivity

Synthesis of Chiral Piperazines via Hydrogenation of Pyrazines Activated by Alkyl Halides

A facile method has been developed for the synthesis of chiral piperazines through Ir-catalyzed hydrogenation of pyrazines activated by alkyl halides, giving a wide range of chiral piperazines including 3-substituted as well as 2,3- and 3,5-disubstituted ones with up to 96% ee. The high enantioselectivity, easy scalability, and concise drug synthesis demonstrate the practical utility.

Chiral phosphoric acid-catalyzed asymmetric transfer hydrogenation of 3-trifluoromethylthioquinolines

A chiral phosphoric acid-catalyzed asymmetric transfer hydrogenation of 3-trifluoromethylthioquinolines was developed, providing chiral 2,3-disubstituted 1,2,3,4-tetrahydroquinoline derivatives containing a stereogenic trifluoromethylthio group with up to 99% enantioselectivity.

Palladium-catalyzed asymmetric hydrogenation of 3-phthalimido substituted quinolines

Homogeneous Pd-catalyzed asymmetric hydrogenation of 3-phthalimido substituted quinolines was successfully developed, providing facile access to chiral substituted tetrahydroquinolines bearing two contiguous stereogenic centers with up to 90% ee.

A convergent rhodium-catalysed asymmetric synthesis of tetrahydroquinolines

Rh-catalysed conjugate additions of 2-aminophenyl boronic acid derivatives were exploited in diastereoselective and asymmetric syntheses of tetrahydroquinolines. In both cases, combinatorial variation of the substitution of the tetrahydroquinoline ring system was possible.

Self-Assembly of a Library of Polyborate Chiral Anions for Asymmetric Catalytic Quinoline Reduction

The 'template' polyborate BOROX catalysts are shown to mediate the asymmetric transfer hydrogenation of 2-quinolines. The rapid and simple generation of a large family of BOROX catalysts with significantly altered asymmetric pockets is described. A transition state model that explains the enantioselectivity is proposed.

Enantioselective synthesis of 4,5,6,7-tetrahydroindoles via olefin cross-metathesis/intramolecular Friedel–Crafts alkylation reaction of pyrroles

A sequential catalysis involving olefin cross-metathesis/asymmetric intramolecular Friedel–Crafts alkylation of pyrrole derivatives has been developed.

Catalytic asymmetric hydrogenation of quinoline carbocycles: unusual chemoselectivity in the hydrogenation of quinolines

A chiral PhTRAP–ruthenium catalyst selectively hydrogenates the quinoline carbocycles to afford 5,6,7,8-tetrahydroquinolines with up to 91 : 9 er.

Engineering ligands on the Au center: discovering broadly applicable gold catalysis with high turnover numbers

The research groups of Hammond/Xu and Zhang report the discovery of new ligands for gold catalysis.

Chiral phosphoric acid-catalyzed asymmetric transfer hydrogenation of quinolin-3-amines

A chiral phosphoric acid catalyzed asymmetric transfer hydrogenation of aromatic amines, quinolin-3-amines, was successfully developed with up to 99% ee. To supplement our previous work on the Ir-catalyzed asymmetric hydrogenation of 2-alkyl substituted quinolin-3-amines, a number of 2-aryl substituted substrates were reduced to provide a series of valuable chiral exocyclic amines with high diastereo- and enantioselectivities.

A general ligand design for gold catalysis allowing ligand-directed anti-nucleophilic attack of alkynes

Most homogenous gold catalyses demand ≥0.5 mol % catalyst loading. Due to the high cost of gold, these reactions are unlikely to be applicable in medium or large scale applications. Here we disclose a novel ligand design based on the privileged biphenyl-2-phosphine framework that offers a potentially general approach to dramatically lowering catalyst loading. In this design, an amide group at the 3’ position of the ligand framework directs and promotes nucleophilic attack at the ligand gold complex-activated alkyne, which is unprecedented in homogeneous gold catalysis considering the spatial challenge of using ligand to reach antiapproaching nucleophile in a linear P-Au-alkyne centroid structure. With such a ligand, the gold(I) complex becomes highly efficient in catalyzing acid addition to alkynes, with a turnover number up to 99,000. Density functional theory calculations support the role of the amide moiety in directing the attack of carboxylic acid via hydrogen bonding.

When gold meets chiral Brønsted acid catalysts: extending the boundaries of enantioselective gold catalysis

This review describes the development in the use of Au(i)/Brønsted acid binary catalytic systems to enable an enantioselective transformation in one-pot that cannot be achieved by gold catalysts alone.

Strategic innovation in the total synthesis of complex natural products using gold catalysis

This review has been organized from the perspective of synthetic target families, with emphasis on the use of gold-catalyzed transformations and cascade reactions that significantly increase molecular complexity.

Facile construction of three contiguous stereogenic centers via dynamic kinetic resolution in asymmetric transfer hydrogenation of quinolines

An efficient and facile route to chiral tetrahydroquinolines with three contiguous stereogenic centers via a dynamic kinetic resolution process has been successfully developed by using chiral phosphoric acid as catalyst and Hantzsch ester as the hydrogen source with up to 89% ee.

A combined continuous microflow photochemistry and asymmetric organocatalysis approach for the enantioselective synthesis of tetrahydroquinolines

A continuous-flow asymmetric organocatalytic photocyclization-transfer hydrogenation cascade reaction has been developed. The new protocol allows the synthesis of tetrahydroquinolines from readily available 2-aminochalcones using a combination of photochemistry and asymmetric Brønsted acid catalysis. The photocylization and subsequent reduction was performed with catalytic amount of chiral BINOL derived phosphoric acid diester and Hantzsch dihydropyridine as hydrogen source providing the desired products in good yields and with excellent enantioselectivities.