Maksim A. Boichenko, Timur P. Tikhonov, Vitaly V. Shorokhov, Danila S. Lebedev, Ernal R. Gaiazov, Sergey S. Zhokhov, Victor A. Tafeenko, Nina K. Ratmanova, Igor V. Trushkov, Ivan A. Andreev, Olga A. Ivanova
We report the direct synthesis of densely substituted spiroannulated cyclobutanes from indane-1,3-dione-based activated alkenes or their analogs and sulfur ylides under mild, Lewis acid-free conditions. The transformation proceeds through a Corey–Chaykovsky cyclopropanation that furnishes highly strained donor–acceptor spirocyclopropanes, followed by their (3 + 1)-annulation with stabilized sulfonium ylides that can be conducted in a telescoped or one-pot fashion. Preliminary mechanistic studies allowed a better understanding of the origin of both the observed high reactivity and diastereoselectivity.