Asymmetric Organocatalytic [4 + 1] Annulations: Enantioselective Construction of Multifunctionalized Spirocyclopentane Oxindoles Bearing α,α-Disubstituted α-Amino-β-keto Esters

Access to densely functionalized spirocyclopentenonyl oxindole frameworks via aza- and carbo-Piancatelli rearrangement

A new strategy for access to spirocyclopentenonyl oxindole frameworks is disclosed. Suitably anchored furfuryl alcohol at C3 of an oxindole was used for the aza-Piancatelli rearrangement, which furnished spirocyclic aminocyclopentenone frameworks with catalytic phosphomolybdic acid. The scope of the transformation was extended to the carbo-Piancatelli rearrangement with various indole derivatives.

Phase-Transfer-Catalyzed Asymmetric Annulations of Alkyl Dihalides with Oxindoles: Unified Access to Chiral Spirocarbocyclic Oxindoles

A general phase-transfer-catalyzed asymmetric (n+1) (n = 4 or 5) annulation reaction, featuring the direct coupling of simple oxindoles with alkyl dihalides that are allylic/benzylic and non-allylic/benzylic, has been developed to provide previously inaccessible cyclopentane- and cyclohexane-fused spirooxindole scaffolds with high yields and enantioselectivities (88-95% ee). Along with a broad scope and mild conditions, the new protocol also enables a two-step and gram-scale synthesis of the core of the drug ubrogepant.

Lewis acid-catalyzed [3 + 2] annulations of oxindole based spirocyclic donor-acceptor cyclopropanes with ynamides

[3 + 2] annulations of oxindole based spirocyclic donor-acceptor cyclopropanes and ynamides catalyzed by copper triflate have been developed for the synthesis of biologically important spirocyclopenteneoxindoles. These reactions tolerated a wide scope of substrates and provided the desired products in good to high yields (up to 90%) with up to >40 : 1 diastereoselectivities under mild conditions.

Divergent Synthesis of Bicyclo[3.2.1]octenes and Cyclohexenes via Catalytic Annulations of Nazarov Reagent and Vinyl 1,2-Diketones

Bicyclo[3.2.1]octanes and related structures are unique units that widely exist in natural products, but the rapid and stereoselective construction of this skeleton is a challenging issue. We report the stereodivergent synthesis of bicyclo[3.2.1]octenes using Nazarov reagents and alkenyl 1,2-diketones with Brønsted base catalysis under mild conditions. Both stereoisomers of the bridged products can be obtained by tuning the reaction conditions, and cyclohexene product can also be selectively formed.

Organocatalytic Aza-Michael/Michael Cyclization Cascade Reaction: Enantioselective Synthesis of Spiro-oxindole Piperidin-2-one Derivatives

A simple, direct, and highly enantioselective synthesis of spiro-oxindole piperidin-2-one derivatives was achieved through an aza-Michael/Michael cyclization cascade sequence using a squaramide catalyst. The desired products were obtained in excellent yields (up to 99%) and good to high stereoselectivities (up to >20:1 dr and up to 99% ee) under mild conditions.

Palladium-catalysed 5-endo-trig allylic (hetero)arylation

A palladium-catalysed intramolecular allylic (hetero)arylation strategy for the synthesis of fused cyclopentenes incorporated with all-carbon quaternary and spiro centres is described. The method is straightforward, shows broad scope, proceeds in synthetically useful yields, and provides a rare means to construct complex cyclopentanoids. The reaction is believed to involve a kinetically unfavourable 5-endo-trig carbocyclisation of the tethered (π-allyl)palladium system. Further, this method was successfully applied as the key step in the total synthesis of diterpene natural products taiwaniaquinone H and dichroanone.

Coumarin-3-formylpyrazoles as 3-carbon synthons in cyclocondensation for the synthesis of spiro-fused pentacyclic spirooxindoles

Coumarin-3-formylpyrazoles have been synthesized and applied as 3-carbon synthons in reaction with 3-hydroxyoxindoles by using DABCO as the catalyst. A range of structurally diverse spiro-fused pentacyclic spirooxindoles, bearing a spirooxindole-γ-lactone and a 3,4-dihydrocoumarin substructure, could be smoothly obtained in good to excellent yields (up to 99%) with excellent diastereoselectivities (all cases >20 : 1 dr). The asymmetric version of this tandem reaction was preliminarily investigated by using chiral organocatalysts.

Enantioselective aryl–aryl coupling facilitated by chiral binuclear gold complexes

The first example of highly enantioselective aryl–aryl coupling mediated by chiral gold complexes is reported.

Lewis acid catalyzed annulation of spirocyclic donor–acceptor cyclopropanes with exo-heterocyclic olefins: access to highly functionalized bis-spirocyclopentane oxindole frameworks

Oxindole-activated spiro-DAC is used as synthon to prepare complex bis-spirocyclopentane oxindole frameworks via ring-enlargement.

Pd(ii), Ni(ii) and Co(ii)-catalyzed enantioselective additions of organoboron reagents to ketimines

This feature article highlights the development of Pd(ii), Ni(ii), and Co(ii)-catalyzed asymmetric additions of organoboron reagents to ketimines.

Diastereoselective construction of pyrrolo[2,1-a]isoquinoline-based bispirooxindoles through a three-component [3 + 2] cycloaddition

An efficient and highly diastereoselective three-component one-pot [3 + 2] cycloaddition of isatins, 1,2,3,4-tetrahydroisoquinolines and methyleneindolinones has been developed to afford a wide range of pyrrolo[1,2-a]isoquinoline-based bispirooxindoles in up to 91% yields.