Selective C3-Allylation and Formal [3 + 2]-Annulation of Spiro-Aziridine Oxindoles: Synthesis of 5'-Substituted Spiro[pyrrolidine-3,3'-oxindoles] and Coerulescine

Brønsted acid- and/or Lewis acid-catalyzed selective C3-allylation and formal [3 + 2]-annulation of spiro-aziridine oxindoles with allylsilanes have been demonstrated to deliver direct access to 3-allyl-3-aminomethyl oxindoles and 5-silyl methyl spiro[pyrrolidine-3,3'-oxindoles], respectively. The acid-catalyzed methods do not provide any stereoselectivity when chiral spiroaziridines are used. However, the reaction of nonracemic sprioaziridines with allyl-Grignard reagent under catalyst-free conditions afforded 3-allyl-3-aminomethyl oxindoles with good stereoselectivity (ee up to 80%). The allylation protocol is utilized for the short synthesis of coerulescine and various 5'-substituted spiro[pyrrolidine-3,3'-oxindoles].

Access to 3,3'-disubstituted peroxyoxindole derivatives and α-peroxyamides via azaoxyallyl cation-guided addition of hydroperoxides

Herein, a transition metal-free approach for access to 3,3'-disubstituted peroxyoxindole is disclosed, which harnesses a transient azaoxyallyl cation. This strategy is also applicable to the synthesis of structurally diverse α-peroxycarboxylic acid surrogates. The method exhibits good functional group tolerance and is suitable for generating a library of peroxy-containing compounds.

Dithiocarbamation of spiro-aziridine oxindoles: a facile access to C3-functionalised 3-thiooxindoles as apoptosis inducing agents

Herein, we report the first dithiocarbamation of spiro-aziridine oxindoles involving regiospecific ring-opening by using in situ generated nucleophilic dithiocarbamates as an instant source of sulfur. This approach afforded C3-functionalised-3-thiooxindoles in good to excellent yields with a wide substrate scope under catalyst-free and mild reaction conditions. These compounds were screened for their anticancer activity against a panel of human cancer cell lines, wherein compound 3u exhibited significant cytotoxic activity against human lung cancer cells with an IC50 value of 4.31 ± 1.88 μM. Phase contrast microscopy as well as different staining assays such as acridine orange/ethidium bromide (AO/EB), DAPI and DCFDA demonstrated the induction of apoptosis in A549 lung cancer cells after treatment with compound 3u. In addition, the clonogenic assay and migration assay demonstrated the ability of compound 3u to inhibit colony formation and cell migration, respectively, in A549 cells in a dose-dependent manner.