| Abstract: | The tendency of acylhydrazones to undergo a spontaneous cyclization into 1,3,4‐oxadiazolines has been investigated. Contrary to the literature data, an attempted transformation of isatin cyanoacetylhydrazone in solution generates stereoisomers and not the reported structural isomer oxadiazoline. A similar behavior of the corresponding l‐methyl‐ and l‐acetylisatin derivatives even under acetylation conditions has been found. The crystal structure of the Z isomer of 3‐cyanoacetylhydrazono‐2‐indolinone monohydrate is reported. It contains strong intramolecular hydrogen bond between the hydrazone N H and oxygen atom of the indolinone carbonyl, and in this way the Z isomer over the CN bond is stabilized. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:183–193, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20531 |
