Synthesis of spiro[indazole-3,3'-indolin]-2'-ones and indazolo-[2,3-c]quinazolin-6(5H)-ones from arynes and isatin-derived N-tosylhydrazones

A formal (3+2) annulation reaction between isatin-derived N-tosylhydrazones and o-(trimethylsilyl)aryl triflates allows facile synthesis of spiro[indazole-3,3′-indolin]-2′-ones in high to excellent yields. Furthermore, indazolo[2,3-c]quinazolin-6(5H)-ones could be accessed from the same starting materials in one-pot fashion via an annulation/rearrangement pathway.