Catalytic (5 + 1) cycloaddition of diazooxindoles with imidazolidines to access novel piperazine-spirooxindole frameworks

Abstract

Herein, a catalytic (5 + 1) cycloaddition of diazooxindoles with imidazolidines is described, providing a general and efficient synthetic route to access medicinally attractive piperazine-spirooxindole frameworks in moderate to good yields under rhodium or copper catalysis. Moreover, diverse transformations of the obtained products have been achieved to access more complex and even drug-derived spirooxindoles. Importantly, the asymmetric version has also been realized by employing the combination of Cu(OTf)₂ and SaBOX ligand L5, leading to optically active products with up to 93 : 7 er. This report shows that rhodium and copper are both potent catalysts for this reaction and that copper is more competent than rhodium in catalytic asymmetric reactions involving diazocarbene-ylide intermediates.