Selective Aza Diels–Alder and Domino [4+2]/[2+2] Cycloaddition Reactions of Arynes with <i>N</i>‑Sulfonyl Ketimines

Transition-metal-free inverse electron-demand aza Diels–Alder and domino [4+2]/[2+2] cycloaddition reaction of arynes and <i>N</i>-sulfonyl ketimines has been demonstrated. This novel, mild, and efficient protocol allows rapid access to isothiazole dioxide-fused dihydroquinoline or dihydrocyclobutaquinoline derivatives selectively by simply varying the equivalents of aryne precursors. The application of this method has been amply illustrated in the synthesis of 2,4-diarylquinolines