Oxalic acid, dipotassium salt

Oxalic acid dinitrile. See Cyanogen Oxalic acid, dipotassium salt. See Potassium oxalate... 

The classical preparation16 of this salt involves the reaction of oxalic acid, dipotassium oxalate, and potassium dichromate, in which the reduction Cr(VI) — Cr(IH) is accompanied by complexation. The method described below has chromium in the +3 state in the highly reactive starting material. 

Synonyms Dipotassium oxalate Ethanedioic acid, dipotassium salt Oxalic acid. 

The condensation of sulphamide and diethyl oxalate produces 3,4-dihydroxy-1,2,5-thiadiazole 1,1-dioxide as the dipotassium salt in high yield. The free acid (177) is an excellent precursor for the preparation of other functional derivatives, and for building up fused ring systems incorporating the 1,2,5-thiadiazole 1,1-dioxide structure (see below). The two isomeric benzothiadiazole acetoximes (178) and (179) undergo the Beckmann reaction, resulting in the fission of their carbocyclic ring. This provides an effective synthesis of novel ajS-unsaturated 1,2,5-thiadiazoles (180 X = COaH, Y = CR=CHCN X =... 

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