A bifunctional organocatalytic asymmetric formal 4 + 2 cycloaddition reaction of Nazarov reagents and methyleneindolinones afforded spiro4-cyclohexanone-1,3′-oxindoline derivatives with excellent ...enantioselectivity (up to 98% ee).
A little gold goes a long way: As little as 0.01 mol % of chiral gold phosphate is sufficient to afford the asymmetric transfer hydrogenation of quinolines with high stereoselectivity (up to 98 % ...ee). The achiral ligands on gold were found to have considerable effect on the catalytic efficiency.
The first enantioselective dearomatizative spirocyclization of 1‐hydroxy‐N‐aryl‐2‐naphthamide derivatives has been accomplished by chiral organoiodine catalysis to stereoselectively create an ...all‐carbon stereogenic center, providing a straightforward approach to access spirooxindole derivatives in good yields and with high to excellent levels of enantioselectivity. Chiral hypervalent phenyl‐λ3‐iodanes generated in situ from the oxidation of the chiral phenyl iodine actually participate in the asymmetric oxidative dearomatizative spirocyclization reaction.
The all‐C‐ing I: Enantioselective dearomatizative spirocyclization of 1‐hydroxy‐N‐aryl‐2‐naphthamide derivatives is accomplished by chiral organoiodine catalysis to stereoselectively construct an all‐carbon stereogenic center, providing a straightforward approach to access spirooxindole derivatives in good yields and with high to excellent levels of enantioselectivity.
A PdII‐catalyzed asymmetric aminohydroxylation of 1,3‐dienes with N‐tosyl‐2‐aminophenols was developed by making use of a chiral pyridinebis(oxazoline) ligand. The highly regioselective reaction ...provides direct and efficient access to chiral 3,4‐dihydro‐2H‐1,4‐benzoxazines in high yield and enantioselectivity (up to 96:4 e.r.). The reaction employs readily available N‐tosyl‐2‐aminophenols as a unique aminohydroxylation reagent and is complementary to known asymmetric aminohydroxylation methods.
Give me a ring: A palladium‐catalyzed asymmetric aminohydroxylation reaction of 1,3‐dienes with N‐tosyl‐2‐aminophenols was developed by employing a chiral pyridinebis(oxazoline) ligand. This reaction furnishes optically active 3,4‐dihydro‐2H‐1,4‐benzoxazines in high yields and with high levels of regio‐ and stereoselectivity.
A combination of either ruthenium(II) or rhodium(II) complexes and quinine‐derived squaramide enables 3‐diazooxindoles, indoles, and nitroalkenes to undergo highly efficient asymmetric ...three‐component reactions, thus affording optically active 3,3′‐bis(indole)s through a consecutive CC bond‐forming sequence, which turned out to be applicable to the facile total synthesis of (−)‐folicanthine.
Square deal: A combination of either ruthenium(II) or rhodium(II) complexes and quinine‐derived squaramide enables 3‐diazooxindoles, indole, and nitroalkenes to undergo a highly efficient asymmetric three‐component reaction. Based on this metal/organo relay catalysis, a total synthesis of (−)‐folicanthine was accomplished in seven steps with 14.5 % overall yield.
Brønsted acids of anionic chiral CoIII complexes act as bifunctional phase‐transfer catalysts to shuttle the substrates across the solvent interface and control stereoselectivity. The diastereomeric ...chiral CoIII‐templated Brønsted acids, with the same chiral ligands, enabled a switch in the enantioselective bromoaminocyclization of olefins to afford the two enantiomers of 2‐substituted pyrrolidines with high enantioselectivities (up to 99:1 e.r.).
Flip of the switch: Brønsted acids of anionic chiral CoIII complexes act as bifunctional phase‐transfer catalysts to shuttle the substrates across the solvent interface and control stereoselectivity. The diastereomeric chiral CoIII‐templated Brønsted acids, with the same chiral ligands, enabled a switch in the enantioselective bromoaminocyclization of olefins to afford the two enantiomers of the 2‐substituted pyrrolidines with high stereoselectivities.
Cooperation is key! Chiral Brønsted acid/rhodium(II) cooperative catalysis enabled an enantioselective three‐component aldol‐type reaction of 3‐diazo oxindoles and anilines with glyoxylates to give ...highly functionalized and structurally diverse 3‐amino oxindoles in high stereoselectivity (>20:1 d.r., 99 % ee; see scheme).
Something constructive: The title reaction involving 3‐hydroxyoxindoles gives 3,3′‐disubstituted oxindoles with concomitant generation of an all‐carbon quaternary stereogenic center in high yield and ...excellent enantioselectivity. This reaction enabled the enantioselective construction of hexahydropyrroloindole skeletons and the first catalytic enantioselective total synthesis of (+)‐folicanthine.
The sodium salts of anionic chiral cobalt(III) complexes (CCC−Na+) have been found to be efficient catalysts of the asymmetric Povarov reaction of easily accessible dienophiles, such as ...2,3‐dihydrofuran, ethyl vinyl ether, and an N‐protected 2,3‐dihydropyrrole, with 2‐azadienes. Ring‐fused tetrahydroquinolines with up to three contiguous stereogenic centers were thus obtained in high yields, excellent diastereoselectivities (endo/exo up to >20:1), and high enantioselectivities (up to 95:5 e.r.).
A salty catalyst: The sodium salts of anionic chiral cobalt(III) complexes (CCC−Na+) have been found to be efficient catalysts of the asymmetric Povarov reaction of easily accessible dienophiles with 2‐azadienes. Ring‐fused tetrahydroquinolines with up to three contiguous stereogenic centers were thus obtained in high yields, excellent diastereoselectivities, and high enantioselectivities (TIPS=triisopropylsilyl).
A palladium‐catalyzed asymmetric intramolecular allylic C−H amination controlled by a chiral phosphoramidite ligand was established for the preparation of various substituted chiral ...hydropyrimidinones, the precursors of hydropyrimidines, in high yields with high enantioselectivities. In particular, dienyl sodium N‐sulfonyl amides bearing an arylethene‐1‐sulfonyl group underwent a sequential allylic C−H amination and intramolecular Diels–Alder (IMDA) reaction to produce chiral fused tricyclic tetrahydropyrimidinone frameworks in high yields and with high levels of stereoselectivity. Significantly, this method was used as the key step in an asymmetric synthesis of letermovir.
Getting to the core of it: An asymmetric palladium‐catalyzed intramolecular allylic C−H amination controlled by a chiral phosphoramidite ligand was used to provide efficient access various substituted chiral hydropyrimidines. This methodology was successfully applied to the asymmetric synthesis of letermovir (see scheme; IMDA=intramolecular Diels–Alder reaction).
