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

Merging Ring-Opening 1,2-Metallate Shift with Asymmetric C(sp3)-H Borylation of Aziridines

Chiral secondary alkyl amines with a vicinal quaternary stereocenter are undoubtedly important and ubiquitous subunits in natural products and pharmaceuticals. However, their asymmetric synthesis remains a formidable challenge. Herein, we merge the ring-opening 1,2-metallate shift with iridium-catalyzed enantioselective C(sp3)-H borylation of aziridines to deliver these frameworks with high enantioselectivities. We also demonstrated the synthetic application by downstream transformations, including the total synthesis of two Amaryllidaceae alkaloids, (-)-crinane and (+)-mesmebrane.

Regioselective Brønsted acid catalyzed ring opening of aziridines by phenols and thiophenols; a gateway to access functionalized indolines, indoles, benzothiazines, dihydrobenzo-thiazines, benzo-oxazines and benzochromenes

Brønsted acid catalyzed regioselective ring opening of aziridines by phenols and thiophenols have been reported. Involvement of a series of aziridines with a range of phenols and thiophenols offer the generality of the reported protocol. Completion of the reaction at room temperature within very short time brings the uniqueness of the developed technique. To emphasis on the application of the developed methodology, the products have been used for the further synthesis of a range of useful and novel heterocyclic molecules such as indolines, indoles, benzothiazines, dihydrobenzothiazines, benzo-oxazines and benzochromenes.

Asymmetric Synthesis of Hydrodibenzofurans from Norcaradienes: Kinetic Resolution via [3 + 2] Cycloaddition with Quinones

The catalytic asymmetric [3 + 2] cycloaddition of racemic norcaradienes with quinones to construct multicyclic hydrodibenzofurans was achieved by the use of chiral N,N'-dioxide/metal complex catalysts. Kinetic resolution of norcaradienes accompanied by partial racemization occurred, and one enantiomer in prior acted as the C2 synthon to participate in diastereoselective cycloaddition. An enantiodivergent synthesis via a switch of metal ions was observed when naphthoquinone was used as the partner. DFT calculations revealed the profiles of the cycloaddition processes.

Catalytic asymmetric addition of thiols to silyl glyoxylates for synthesis of multi-hetero-atom substituted carbon stereocenters

A chiral Lewis acid-catalyzed enantioselective addition of thiols to silyl glyoxylates was developed. The reaction proceeds well with a broad range of thiols and acylsilanes, affording the target tertiary chiral α-silyl–α-sulfydryl alcohols with multi-hetero-atom carbon stereocenters in excellent yields (up to 99%) and enantioselectivities (up to 98% ee). A series of control experiments were conducted to elucidate the reaction mechanism.

Enantioselective addition of thiols to silyl glyoxylates for construction of a multi-hetero-atom substituted carbon stereocenter was described.

An Organocatalytic Kinetic Resolution of Aziridines by Thiol Nucleophiles

We report the first organocatalytic kinetic resolution of unactivated aziridines by sulfur nucleophiles with excellent enantioselectivity. A suitable chiral phosphoric acid was found to catalyze the intermolecular ring opening under mild conditions, furnishing a range of highly enantioenriched β-amino thioethers and aziridines, both of which are useful synthetic building blocks.