Converting Strain\nRelease into Aromaticity Loss for\nActivation of Donor–Acceptor Cyclopropanes: Generation of Quinone\nMethide Traps for C‑Nucleophiles

Here, we present a new approach for the activation of\ndonor–acceptor\ncyclopropanes in ring-opening reactions, which does not require the\nuse of a Lewis or Brønsted acid as a catalyst. Donor–acceptor\ncyclopropanes containing a phenolic group as the donor undergo deprotonation\nand isomerization to form the corresponding quinone methides. This\ninnovative strategy was applied to achieve (4 + 1)-annulation of cyclopropanes\nwith sulfur ylides, affording functionalized dihydrobenzofurans. Additionally,\nthe generated <i>ortho</i>- and <i>para</i>-(aza)quinone\nmethides can be trapped by various CH-acids.