Chemistry of Indoles Carrying a Basic Function, Part 31 Synthesis of Spiro[cyclopropane‐1,3′[3H]indol]‐2′(1′H)‐ones with Antihypoxic Effects

Abstract
Hydroxyindolones (1–6, 15–16) were transformed into isatinylidenes (7,9–13, 17–19) by dehydration with 4‐toluenesulfonic acid. The dimer‐type compounds (14, 20) were also isolated in a few cases. The obtained isatinylidenes were transformed into 3‐spiro‐cyclopropane‐oxindoles (21–32) with dimethyloxosulfonium methylide. Compound 22 shows protective effects against hypobaric hypoxia and triethyltin induced brain edema.