Highly diastereoselective construction of novel dispiropyrrolo[2,1- a ]isoquinoline derivatives via multicomponent 1,3-dipolar cycloaddition of cyclic diketones-based tetrahydroisoquinolinium N -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.