Catalytic asymmetric synthesis of tetrahydrocarbazoles

This feature article summarises recent advances in catalytic asymmetric synthesis of THCs, with emphases on reaction type and reaction mechanism.

Organocatalytic asymmetric synthesis of tetrahydrocarbazoles via an inverse-electron-demand Diels–Alder reaction of 2,3-indole-dienes with enals

A novel 2,3-indole-diene synthon was designed and first applied to an inverse-electron-demand Diels–Alder reaction to construct tetrahydrocarbazoles with excellent stereoselectivities.

Cupreines and cupreidines: an established class of bifunctional cinchona organocatalysts

Cinchona alkaloids with a free 6'-OH functionality are being increasingly used within asymmetric organocatalysis. This fascinating class of bifunctional catalyst offers a genuine alternative to the more commonly used thiourea systems and because of the different spacing between the functional groups, can control enantioselectivity where other organocatalysts have failed. In the main, this review covers the highlights from the last five years and attempts to show the diversity of reactions that these systems can control. It is hoped that chemists developing asymmetric methodologies will see the value in adding these easily accessible, but underused organocatalysts to their screens.

DABCO catalyzed domino Michael/hydroalkoxylation reaction involving α-alkynyl-β-aryl nitroolefins: excellent stereoselective access to dihydropyrano[3,2-c]chromenes, pyranonaphthoquinones and related heterocycles

The stereoselective (up to ≤96 : 4 Z/E ratio) access to pyrano[3,2-c]chromenes and related scaffolds has been achieved in 72–89% yields via a domino reaction of enolizable cyclic 1,3-dicarbonyls and β-alkynyl nitroolefins.

Organocatalysed Michael addition on arylmethylidenemalonates involving 4-(2-nitrophenyl)acetoacetate: diversity-oriented access to 8,9-dihydropyrido[1,2-a]indol-6(7H)-one and salicylate scaffolds

A diversity-oriented synthesis of 8,9-dihydropyrido[1,2-a]indol-6(7H)-one and salicylate scaffolds was achieved in high yields with excellent diastereoselectivities (≤96 : 4 dr) via an organocatalytic reaction of alkylidene malonates with 4-(2-nitrophenyl) acetoacetate.

A catalyst-free, efficient green MCR protocol for access to functionalized γ-carbolines in water

A catalyst-free green procedure for access to substituted γ-carbolines has been achieved in water with excellent yields via a MCR reaction of 3-formyl indole derivatives, aldehydes with NH₄OAc at room temperature under aerobic conditions.

A remarkable solvent effect on the reaction of 4-hydroxycoumarin with (E)-3-aryl-2-nitroprop-2-enol: Facile synthesis of highly substituted furo/pyrano[3,2-c]chromenes

The solvent dependent reaction of 4-hydroxycoumarin with (E)-3-aryl-2-nitroprop-2-enol has been reported for the synthesis functionalized furo/pyrano[3,2-c]chromenes in water and DMSO media.