Transformation of Isatin 3-Acylhydrazones under Acetylating Conditions: Synthesis and Structure Elucidation of 1,5′-Disubstituted 3′-Acetylspiro[oxindole-3,2′-[1,3,4]oxadiazolines]

Several substituted isatin 3-acylhydrazones (e.g. 1a–k, n, p, t) have been synthesized. Under acetylating conditions they were transformed into selectively acetylated derivatives (e.g., 1l, n, o, q–s) and into the novel, title spiroheterocycles (2a–i). Some side reactions occurring under various acetylating conditions are also discussed.