Rh(I)-catalyzed regio- and enantioselective allylic alkylation of Meldrum’s acid

Chiral Spirobipyridine Synthesis by Cobalt-Catalyzed Enantioselective Double [2 + 2 + 2] Cycloaddition

Chiral spirobiindanes are recognized as the privileged structures in the field of asymmetric catalysis. However, the structurally similar chiral spirobipyridines have not yet been explored as chiral ligands or organocatalysts due to the absence of efficient synthetic methods. Herein, we report a cobalt-catalyzed enantioselective synthesis of spirobipyridines via double [2 + 2 + 2] cycloaddition reaction. Spirobipyridines with ortho- or meta-substituents could be obtained with exclusive regioselectivity and up to 99% ee in the presence of cobalt and bisoxazolinephosphine ligands. Spirobipyridines coordinate with transition metals as chiral ligands. Spirobipyridine dioxides can be applied as chiral organocatalysts in the asymmetric allylation of aldehydes.

Rhodium-Catalyzed Regio- and Enantioselective Allylic Sulfonylation from Sulfonyl Hydrazides

A highly regio- and enantioselective allylic sulfonylation has been developed with rhodium and bisoxazolinephosphine (NPN*) ligands from racemic branched allylic carbonates and readily available sulfonyl hydrazides under neutral conditions. Branch-selective allylic sulfones with a >20:1 branch:linear ratio and >99% ee could be synthesized in ≤96% yield. Both Z and E linear allylic carbonates could also be converted into the same chiral branched allylic sulfones with high regio- and enantioselectivities.

Regio- and Enantioselective Allylic Cyanomethylation by Synergistic Rhodium and Silane Catalysis

Rh/silane-cocatalyzed regio- and enantioselctive allylic cyanomethylation with inert acetonitrile directly has been developed. Addition of a catalytic amount neutral silane reagent as an acetonitrile anion carrier is essential for the success of this reaction. The synthesis of mono- and bis-allylation products can be switched by adjusting the size of substituents on the silane, ligands, and temperature. Chiral homoallylic nitriles could be synthesized in above 20:1 branch/linear ratio, up to 98% yield and >99% ee.

Rh-Catalyzed Regio- and Enantioselective Allylic Phosphinylation

Transition-metal-catalyzed branched and enantioselective allylic substitution of monosubstituted precursors with carbon, nitrogen, oxygen, sulfur, and fluoride nucleophiles has been well-established. However, such a selective carbon-phosphorus bond formation has not been realized probably due to the catalyst deactivation by the strong coordinating nature of phosphinylating reagents. Herein, we report a Rh-catalyzed highly regio- and enantioselective synthesis of allylic phosphine oxides in the presence of a chiral bisoxazoline-phosphine ligand. The application of α-hydroxylalkylphosphine oxides to keep the low concentration of the secondary phosphine oxides is essential for the high yields. The addition of diphenyl phosphoric acid was found to not only activate allylic alcohols but also accelerate the carbon-phosphorus bond formation.

Diastereoselective Synthesis of a cis-1,3-Disubstituted Cyclobutane Carboxylic Acid Scaffold for TAK-828F, a Potent Retinoic Acid Receptor-Related Orphan Receptor (ROR)-γt Inverse Agonist

A scalable synthesis of the cis-1,3-disubstituted cyclobutane carboxylic acid scaffold of TAK-828F (1) has been developed, featuring the diastereoselective reduction of a cyclobutylidene Meldrum's acid derivative with NaBH₄. Controlling acidic impurities was crucial for improving the diastereomeric ratio by recrystallization. Furthermore, reaction optimization and the streamlining of several steps established a scalable synthetic method free from column chromatography purification with an overall yield improved from 23 to 39%.

Rhodium-Catalyzed Regio- and Enantioselective Allylic Amination of Racemic 1,2-Disubstituted Allylic Phosphates

Alkynylphosphines are rarely used as ligands in asymmetric metal catalysis. We synthesized a series of chiral bis(oxazoline)alkynylphosphine ligands and used them in Rh-catalyzed highly regio- and enantioselective allylic amination reactions of 1,2-disubstituted allylic phosphates. Chiral 1,2-disubstituted allylic amines were synthesized in up to 95% yield with >20:1 branched/linear (b/l) ratio and 99% ee from racemic 1,2-disubstituted allylic precursors. The sterically smaller linear alkynyl group on the P atom in the bis(oxazoline)alkynylphosphine ligands was the key to fit the new requirements of the introduction of bulky 2-R' groups.

Rhodium(i)/bisoxazolinephosphine-catalyzed regio- and enantioselective amination of allylic carbonates: a computational study

DFT calculations were performed to investigate the rhodium(i)/bisoxazolinephosphine-catalyzed regio- and enantioselective amination of allylic carbonates.

Rh-Catalyzed diastereo- and linear-selective α-allylation of chiral cycloenamines

In this paper, a Rh-catalyzed diastereoselective α-allylation of cycloenamines is demonstrated.