Hantzschs Synthesis and Related Cyclizations

Synthesis.—HantzscKs Synthesis and Related Cyclizations. The use of various forms of Hantzsch s synthesis continues to account for a large part of the preparative work in this field. The majority of the compounds listed in Table 3 have been obtained by variations of this general route. 

Thiazolidines incorporating a hydroxyamine function (258) are formed directly by the condensation of iV-hydroxythioureas (257) and chloroacetyl chloride. They are isomerized to the 3-aryl-2-hydroxyiminothiazolidin-4-ones (259) by methanolic sodium methoxide. 2,3-Disubstituted thiazolidin-4-ones of type (261) are accessible by the condensation of the appropriate thioamides (260) with bromoacetic ester. l-Acyl-1,3,3-trichloroprop-2-enes (263), showing the usual reactivity of a-chloroketones, react with thiourea to yield 4-substituted 2-amino-5-(2, 2 -dichlorovinyl)-4-hydroxythiazolidines (262). The pyrimidine derivative (264), bearing three thiazolidine nuclei, is formed from trithiobarbituric acid by an application of this synthesis.  

The condensation of thiosemicarbazones and maleic anhydride to thiazole derivatives has been successfully extended to thiocarbono-hydrazones of aromatic aldehydes and acetophenone (265). Their fusion with maleic anhydride affords a series of substituted thiazolidines of type (266).  

Grabenko, L. N. Kulaeva, and P. S. Pelkis, Khim. geterotsikl. Soedinenii, 

188 Y Vvendenskii and N. M. Turkevich, Dopovidi Akad. Nauk Ukrain. R.S.R., 

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