Asymmetric [3+2]-cyclization of α-imino amide surrogates to construct 3,4-diaminopyrrolidine-2,5-diones.

Using newly designed α-imino amide surrogates and azlactones as amphiphilic reactants, catalyzed by a chiral bifunctional guanidine, the construction of chiral 3,4-diaminopyrrolidine-2,5-diones and their derivatives was realized via formal [3+2]-cyclization. The role of guanidine as a multiple hydrogen bond donor was demonstrated by DFT calculations.

Asymmetric Organocatalytic 1,6-Conjugate Addition of para-Quinone Methides Using [1,2]-Phospha-Brook Rearrangement.

Pudovik addition/[1,2]-phospha-Brook rearrangement as an efficient tool for generation of anionic nucleophiles is an attractive strategy for the construction of C-C bonds in organic synthesis. Herein, we report organocatalytic 1,6-conjugate addition of para-quinone methides utilizing Pudovik addition/[1,2]-phospha-Brook rearrangement. Chiral guanidine-sulfonamide catalyzed the three-component reaction efficiently, providing biologically active oxindole/biaryl/phosphorus-based structures in high yields with excellent diastereo- and enantioselectivities. A possible bifunctional catalytic mode was proposed to elucidate the chiral control of this process.

Asymmetric organocatalytic sulfenylation for the construction of a diheteroatom-bearing tetrasubstituted carbon centre.

Catalytic enantioselective sulfenylation to construct diheteroatom-bearing carbon centres was achieved by employing chiral guanidine organocatalysts. This protocol provided a facile route towards the synthesis of α-fluoro-α-sulfenyl-ß-ketoamides, azlactone adducts and α-sulfur-substituted amino acid derivatives in high yields with good to excellent enantioselectivities. A possible working mode was proposed to elucidate the chiral control of the process.

Asymmetric catalytic [4+3] cycloaddition of ortho-quinone methides with oxiranes.

Catalytic enantioselective [4+3] cycloaddition reaction between o-quinone methides and oxiranes was achieved by using a chiral N,N'-dioxide/TbIII complex as the catalyst, affording medium-sized hydrodioxepine derivatives in high yields (up to 99%) with good to excellent diastereo-(up to 94 : 6 dr) and enantioselectivities (up to 97% ee). The topographic steric maps and distribution of the buried volume (% VBur) of the catalysts via Cavallo's SambVca 2 tool were collected to effectively represent the chiral pocket of metal complexes of chiral N,N'-dioxides.

Kinetic Resolution of Aziridines via Catalytic Asymmetric Ring-Opening Reaction with Mercaptobenzothiazoles.

A highly efficient kinetic resolution of racemic 2-acyl-3-aryl-N-tosylaziridines is achieved through a chiral Lewis acid promoted ring-opening reaction with 2-mercaptobenzothiazoles as the nucleophiles. The chiral N,N'-dioxide-lanthanum complex as catalyst and the 2-mercaptobenzothiazoles as active sulfur nucleophiles are the keys to the success of the reaction. A variety of enantioenriched ß-amino thioethers and aziridines are obtained in good yields with good ee values.