Selective Aza Diels-Alder and Domino [4+2]/[2+2] Cycloaddition Reactions of Arynes with N-Sulfonyl Ketimines.

Transition-metal-free inverse electron-demand aza Diels-Alder and domino [4+2]/[2+2] cycloaddition reaction of arynes and N-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.