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5-chloro-3-hydroxyisothiazole can be synthesized from 3,3'-disulfanediyldipropionic acid and Thionyl chloride in three steps. In particular, in the last step, 5-chloro isothiazolone derivatives (5-chloro-3-hydroxyisothiazole) were the predominant products when the ratio of sulfuryl chloride/amide was 3:1 while with the relevant ratio of 1:1, the 5-unsubstituted analogs were the predominant products[1].

[1] Khalaj A, et al. Synthesis and antibacterial activity of 2-(4-substituted phenyl)-3(2H)-isothiazolones. European Journal of Medicinal Chemistry, 2004; 39: 285–290.