Mechanochemical Bis-Spirocyclopropanation Reaction and Ring Rearrangement to 1-Oxaspiro[4.5]decadienones

Bis-spirocyclopropanation is a very important reaction, which has been less explored. Herein, we describe a bis-spirocyclopropanation reaction from p-quinone methides and readily available active methylene compounds under mechanochemical liquid-assisted grinding (LAG). This protocol allows the synthesis of a diverse range of bis-spirocyclopropanes and spiro-cyclopropanes bearing two contiguous quaternary centers. Further, we advanced this strategy to direct access to fused oxaspirocyclodecadienone derivatives in excellent yields under the same milling conditions. Besides the green synthetic features attributed to this mechanochemical milling, the wide substrate scope, reaction yields, gram-scale synthesis, and postsynthetic modifications strengthen the eminence of the protocol.