The reaction between α-halo ketones and different pyridazinethiones was investigated. It was found that, depending on reaction conditions, the reaction can lead to keto sulfides 2 or hhdroxythiazolinium salts 4. The five-membered ring of the latter is easily cleaved and compounds are converted into keto sulfides 2, whereas in the presence of concentrated sulfuric acid they aromatize to thiazolium salts 3. These are also obtainable directly from 2. © 1969, American Chemical Society. All rights reserved.