An expedient approach for the regio- and stereoselective synthesis of novel spiroindolizidines via [3+2] cycloaddition

Highly diastereoselective construction of novel dispiropyrrolo[2,1-a]isoquinoline derivativesviamulticomponent 1,3-dipolar cycloaddition of cyclic diketones-based tetrahydroisoquinoliniumN-ylides

In the quest for new heterocyclic scaffolds exhibiting potentially biological activities for medicinal chemistry, a multicomponent 1,3-dipolar cycloaddition reaction of tetrahydroisoquinolinium N-ylides, generated in situ from cyclic diketones and isoquinoline, and (E)-3-arylidene-1-phenyl-pyrrolidine-2,5-diones has been developed. This route provides workable access to dispiropyrrolo[2,1-a]isoquinoline-fused pyrrolidine-2,5-diones bearing two adjacent spiro-carbons. An unprecedented regioselectivity was observed in this 1,3-dipolar cycloaddition, leading to the construction of a novel dispirooxindole skeleton. The structure and relative stereochemistry of the spiranic adducts have been confirmed by three X-ray diffraction studies. To reinforce the observed regio- and stereoselectivity of the [3+2] cycloaddition, calculations using the DFT approach at the B3LYP/6-31G(d,p) level were carried out. It was found that this reaction affords the kinetic products.

A new series of dispiropyrrolo[2,1-a]isoquinoline derivatives was synthesized by multicomponent 1,3-dipolar cycloaddition reaction of tetrahydroisoquinolinium N-ylides and (E)-3-arylidene-1-phenyl-pyrrolidine-2,5-diones.

Diastereoselective synthesis of dispirooxindoles via [3+2] cycloaddition of azomethine ylides to 3-phenacylideneoxindoles and evaluation of their cytotoxicity

The three-component reaction of 1,2,3,4-tetrahydroisoquinoline, isatins and 3-phenacylideneoxindoles in refluxing ethanol afforded dispiro[indoline-3,1'-pyrrolo[2,1-a]isoquinoline-3',3'-indolines] (4a-4x) in good yields via 1,3-dipolar cycloaddition of in situ generated azomethine ylide with the exocyclic double bond of 3-phenacylideneoxindoles. 1H NMR spectra and single crystal structures indicated the reaction has high regioselectivity and diastereoselectivity. Furthermore, their biological activities have been preliminarily demonstrated by in vitro evaluation against mouse breast cancer cells 4T1 and human liver cancer cells HepG2 by MTT assay. The results demonstrated that some of the compounds showed cytotoxicities to cell lines of 4T1 and HepG2, and indicated that novel spirooxindoles may become potential lead compounds for further biological screenings of their medicinal applications.

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.