Thiazolidinone dioxides

Diphenylketene (70) undergoes reaction with diisopropylcarbodiimide in liquid sulfur dioxide to give a near quantitative yield of 71 the results suggest a two-step process via a 1,4-dipolar intermediate similar to 68.92 Phenylalkylketenes similarly react with Schiff bases in liquid sulfur dioxide, giving only the mww-thiazolidinone 1,1-dioxides (72).93... 

Gaul, R. J., and W. J. Fremuth Sulfur heterocycles 11. 3-aryl- and 3-Alkyl-2-thiazolidinone 1,1-Dioxides New Class of Cyclic Sulfones. J. org. Chem. 26. 5103 (1961). 

C5H6N2O2S, 4-Carboxylato-L-thiazolidinehydantoin, 46B, 391 C5H6N2O3S, 2-Amino-4-thiazolidinone-5-acetic acid, 38B, 386 CsH7NOS2r 3-Methyl-4-oxo-1,3-thiazine-2-thione, 38B, 386 C5H7N5O2S, 7-Amino-3-methyl-4H-imidazo[2,3-c](1,2,6)thiadiazine 5,5-dioxide, 43B, 471... 

The condensation of benzalaniline and keten to a thiazolidinone 1,1-dioxide in liquid sulphur dioxide (see these Reports, Vol. 1, p. 405) has been extended to keto-ketens (219) of the two theoretically possible isomers (220) and (221), only the trans-form is produced. The configuration was determined by an X-ray analysis in one case (R = i-C3H7), and full structural details were given. 

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