Modular enantioselective access to β-amino amides by Brønsted acid-catalysed multicomponent reactions

Acid-Catalyzed Highly Enantioselective Synthesis of α-Amino Acid Derivatives from Sulfinamides and Alkynes

An enantioselective difunctionalization of activated alkynes using chiral sulfinamide reagents is developed. It is an atom and chirality transfer process that allows for the modular synthesis of optically active α-amino acid derivatives under mild conditions. The reaction proceeds through an acid-catalyzed [2,3]-sigmatropic rearrangement mechanism with predictable stereochemistry and a broad scope.

Modular Assembly of 2-Aminoaniline Derivatives by Merging Hydroxylamine-Passerini and Hetero-Cope Rearrangement

A metal-free three-component protocol that combines a hydroxylamine-Passerini reaction and hetero-Cope rearrangement was realized, which enables the modular assembly of a wide range of structurally new and interesting 2-aminoanilines bearing an α-hydroxyamide substructure.

Ir/Zn-cocatalyzed chemo- and atroposelective [2+2+2] cycloaddition for construction of C─N axially chiral indoles and pyrroles

Here, an Ir/Zn-cocatalyzed atroposelective [2+2+2] cycloaddition of 1,6-diynes and ynamines was developed, forging various functionalized C─N axially chiral indoles and pyrroles in generally good to excellent yields (up to 99%), excellent chemoselectivities, and high enantioselectivities (up to 98% enantiomeric excess) with wide substrate scope. This cocatalyzed strategy not only provided an alternative promising and reliable way for asymmetric alkyne [2+2+2] cyclotrimerization in an easy handle but also settled the issues of previous [Rh(COD)2]BF4-catalyzed system on the construction of C─N axial chirality such as complex operations, limited substrate scope, and low efficiency. In addition, control experiments and theoretical calculations disclosed that Zn(OTf)2 markedly reduced the barrier of migration insertion to significantly increase reaction efficiency, which was distinctly different from previous work on the Lewis acid for improving reaction yield through accelerating oxidative addition and reductive elimination.

Enantioselective Access to Chiral 2,5-Diketopiperazines via Stereogenic-at-Cobalt(III)-Catalyzed Ugi-4CRs/Cyclization Sequences

An asymmetric synthesis of chiral 2,5-diketopiperazines by the Ugi-4CR/cyclization is exhibited. The employment of catalytic anionic chiral Co(III) complexes delivered α-propiolyl aminoamides in high yields with excellent enantioselectivities (31 examples, up to 95% ee). The following treatment of Ugi-adducts with PPh3 leads to chiral 2,5-DKPs without significant loss of enantioselectivities (26 examples, up to 91% ee).

Pseudo-Diastereodivergent Synthesis of Chiral Fluorenes Bearing Bis-1,3-Nonadjacent Stereogenic Centers via Organocatalytic Desymmetrization of meso-Epoxides

We report an enantio- and diastereodivergent synthesis of enantioenriched fluorenes bearing bis-1,3-nonadjacent stereocenters with broad substrate scope and high enantioselectivity (up to 99% ee) under low catalyst loading (0.1 mol %). The key to the success of this method is the pseudo-diastereodivergent desymmetrization of stereoisomers of meso-epoxides enabled by the same organocatalyst. Furthermore, some of the chiral fluorenes obtained exhibit high fluorescence quantum yields (up to 76.6%), as evidenced by photophysical properties studies.

Asymmetric Acyclic 1,3-Difunctionalization of Vinyl Carbenes via Site-Selective Vinylogous Mannich-Type Interception of Oxonium Ylides

A novel and highly stereoselective acyclic 1,3-difunctionalization of vinyl metal carbene species has been developed via Rh(II)/chiral phosphoric acid co-catalyzed three-component reactions of vinyldiazoacetates with alcohols and imines. This innovative approach features excellent regio-, diastereo-, and enantioselectivities, demonstrating a broad scope and functional group compatibility. Notably, this is the first example of three-component asymmetric acyclic 1,3-difunctionalization with in situ-formed vinyl metal carbenes.