Synthesis of Spiro[indazole-3,3′-indolin]-2′-ones via [3 + 2] Dipolar Cycloaddition of Arynes with 3‑Diazoindolin-2-ones and Indazolo[2,3‑c]quinazolin-6(5H)‑ones by Subsequent Thermal Isomerization

An efficient protocol for facile construction of spiro­[indazole-3,3′-indolin]-2′-ones was developed via [3 + 2] dipolar cycloaddition of arynes with 3-diazoindolin-2-ones under mild conditions in excellent yields. Subsequent thermal isomerization of the spiro­[indazole-3,3′-indolin]-2′-ones readily afforded indazolo­[2,3-c]­quinazolin-6­(5H)-ones.