A wide range of 2,3-disubstituted quinoxalines have been successfully hydrogenated with H₂ using borane catalysts to produce the desired tetrahydroquinoxalines in 80–99 % yields with excellent cis selectivity. Significantly, the asymmetric reaction employing chiral borane catalysts generated by the in situ hydroboration of chiral dienes with HB(C₆F₅)₂ under mild reaction conditions has also been achieved with up to 96 % ee, and represents the first catalytic asymmetric system to furnish optically active cis-2,3-disubstituted 1,2,3,4-tetrahydroquinoxalines.

A wide range of 2,3-disubstituted quinoxalines have been successfully hydrogenated with H₂ using borane catalysts to produce the desired tetrahydroquinoxalines in 80–99 % yields with excellent cis selectivity. Significantly, the asymmetric reaction employing chiral borane catalysts generated by the in situ hydroboration of chiral dienes with HB(C₆F₅)₂ under mild reaction conditions has also been achieved with up to 96 % ee, and represents the first catalytic asymmetric system to furnish optically active cis-2,3-disubstituted 1,2,3,4-tetrahydroquinoxalines.

The stereoselective hydrogenation of alkynes to alkenes is an extremely useful transformation in synthetic chemistry. Despite numerous reports for the synthesis of Z-alkenes, the hydrogenation of alkynes to give E-alkenes is still not well resolved. In particular, selective preparation of both Z- and E-alkenes by the same catalytic hydrogenation system using molecular H₂ has rarely been reported. In this paper, a novel strategy of using simple alkenes as promoters for the HB(C₆F₅)₂-catalyzed metal-free hydrogenation of alkynes was adopted. Significantly, both Z- and E-alkenes can be furnished by hydrogenation with molecular H₂ in high yields with excellent stereoselectivities. Further experimental and theoretical mechanistic studies suggest that interactions between H and F atoms of the alkene promoter, borane intermediate, and H₂ play an essential role in promoting the hydrogenolysis reaction.

Chiral olefins have recently emerged as among the most promising ligands for asymmetric catalysis. In the past nearly ten years, significant advances have been made in developing ligands, including diene and heteroatom/olefin hybrid ligands, and exploring their applications in challenging metal-catalyzed asymmetric reactions. Especially in some cases, chiral olefin ligands have an obvious advantage over some conventional chiral ligands in terms of activity and selectivity. Besides the most often studied rigidly bicyclic dienes, readily accessible chiral-chain dienes with flexible frameworks and two terminal olefins as coordinating groups have also proven to be effective for achieving high levels of enantioselectivity in transition-metal-catalyzed asymmetric reactions. Moreover, the terminal olefins can be combined with phosphorus atoms on suitable chiral skeletons for the development of novel phosphorus/olefin (P/olefin) hybrid ligands, which have high activity and selectivity in Pd-catalyzed asymmetric transformations. Significantly, sulfur/olefin (S/olefin) hybrid ligands have been successfully explored and applied in a range of Rh-catalyzed asymmetric transformations. This Focus Review will mainly discuss the synthesis of recently developed chiral-chain diene ligands, phosphorus/terminal-olefin hybrid ligands, and sulfur/olefin hybrid ligands, and their application in asymmetric catalysis.

A variety of acyclic chiral dienes were synthesized in a single step via palladium(0)-catalyzed asymmetric allylic and homoallylic CH diamination of terminal olefins. The applications of such simple dienes as steering ligands for rhodium(I)-catalyzed asymmetric 1,4-additions afforded the corresponding adducts in excellent yields and up to 85% ee.