Herein, a previously unreported Fischer’s base reactants serving as useful 2C building blocks in (3+2) cycloaddition reactions to build a library of bispiro[Fischer base-oxindole] hybrids is described. These structurally intriguing products containing three adjacent quaternary stereocentres were smoothly afforded in up to 82% yield, >20:1 dr under catalyst-free condition. Notably, the present protocol firstly employs 3-isothiocyanato oxindole serving as an acceptor and then as a donor in the formal (3+2) cycloadditions, allowing a practical, straightforward access to structurally diverse cycloadducts. This work expands the applicability scope of 3-isothiocyanato oxindoles, which was limited to behaving as donor/acceptor-based synthons in cycloadditions in previous work.

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