Bicarbonate-binding catalysis for the enantioselective desymmetrization of keto sulfonium salts

Herein, an enantioselective desymmetrization of cyclic keto sulfonium salts through enantioselective deprotonation/ring opening process by anion-binding catalysis is presented. We report a squaramide/HCO3- complex as catalytic active species which is able to stereo-differentiate two enantiomeric protons, triggering the ring opening event taking advantage of the great tendency of sulfonium salts to act as leaving groups. Thus, this desymmetrization methodology give rise to β-methylsulfenylated sulfa-Michael addition type products with excellent yields and very good enantioselectivities. The bifunctional organocatalyst has been demonstrated to be capable of activating simultaneously the base and the keto sulfonium salt by DFT calculations and experimental proofs.

Bifunctional Iminophosphorane Catalyzed Amide Enolization for Enantioselective Cyclohexadienone Desymmetrization

The organocatalytic enolization of 2-arylacetamides, followed by an enantioselective intramolecular conjugate addition to tethered 2,5-cyclohexadienones, yielding 3D fused N-heterocycles, is described. The transformation represents the first strong activating group-free activation of carboxamides via α-C-H deprotonation in a metal-free, catalytic, and enantioselective reaction, and is achieved by employing a bifunctional iminophosphorane (BIMP) superbase.

Desymmetrization of Cyclohexadienones through Phase-Transfer-Catalyzed Stereoselective Intramolecular Aza-Michael Addition with Chiral Sulfinamide Nucleophiles

This paper reports the desymmetrization of cyclohexadienones through stereoselective intramolecular aza-Michael addition with a tethered chiral sulfinamide nucleophile. The reaction was facilitated by phase-transfer catalysis and produced various nitrogen-containing bicyclic compounds with a yield of up to 93% and a diastereomeric ratio of up to >20:1.

Asymmetric synthesis of spirocyclic isobenzofuranones via a squaramide-catalysed sulfa-Michael desymmetrisation reaction

Enantioselective synthesis of spirocyclohexenone isobenzofuranones has been achieved through an organocatalysed sulfa-Michael desymmetrisation reaction. A cinchona-derived squaramide effectively promotes the desymmetrisation of spirocyclic 2,5-cyclohexadienone isobenzofuranones via the controlled addition of various aryl thiols to generate two vicinal stereocenters with perfect diastereoselectivities and up to very good enantioselectivities.

Asymmetric Synthesis of Cyclohexenone-Fused Isochromans via Quinidine-Catalyzed Domino Peroxyhemiacetalization/Oxa-Michael Addition/Desymmetrization Sequence

A highly enantio- and diastereoselective synthesis of highly functionalized isochromans was achieved through an organocatalyzed domino reaction. Quinidine as the catalyst initiates a peroxyhemiacetalization/oxa-Michael/desymmetrization domino sequence between various 2,5-cyclohexadienone-tethered aryl aldehydes with hydroperoxides to generate the single diastereomers of isochromans appended with a cyclohexenone ring bearing three vicinal stereocenters in good yields and high enantioselectivities under ambient reaction conditions.