BISTHIOSEMICARBAZONES OF 2,4-PENTANEDIONE ARE PYRAZOLINES

Attempts to prepare 2,4-bisthiosemicarbamoylpentanediones 1 via litera ture precedent from 2,4-pentanedione and three different thiosemicarba zides resulted instead in the formation of cyclic pyrazolines 5. The p reparation was attempted with thiosemicarbazide, 4-methylthiosemicarba zide, and 4-ethylthiosemicarbazide, respectively. A single-crystal X-r ay structure study of the product from 4-methylthiosemicarbazide confi rmed the pyrazoline structure. This observation serves to correct earl ier misassignments of structure.