3-Pyrazolin-5-selenones

A few halogenated 3-pyrazolin-5-thiones are known (Table XVIII). These are prepared from the methyl chlorides of 3- or 4,5-dichloro-pyrazole by reaction with sodium sulfide or potassium hydrogen sulfide.795,981 Michaelis988,992 has reported that 3-pyrazolin-5-selenones form dichlorides and di- and tetrabromides when treated with chlorine or bromine. No specific structures were suggested. 

Although comparatively little has been published concerning the properties and reactions of 3-pyrazolin-5-thiones and -5-selenones, it is apparent that in general they are very similar to the comparable oxo... 

---