Yield:75423-15-3 94.87%

Reaction Conditions:

with hydrazine hydrate monohydrate in ethanol;Reflux;

Steps:

1 Embodiment 1 Synthesis of Intermediate 4-methyl -1, 2, 3-thiadiazol-5-carbohydrazide III

In 100 ml round-bottom flask, add 4-methyl -1, 2, 3-thiadiazol-5-carboxylic acid ethyl ester 1.0 g, in other words, 5.80 millimole, 30 ml of ethanol as the solvent; dropping slowly under the normal temperature condition 0.44 g of hydrazine hydrate, in other words, 8.70 mmol, after dripping slowly system heating to reflux, TLC detection; after the reaction is ended, concentrated under reduced pressure to remove the solvent to obtain the intermediate 4-methyl -1, 2, 3-thiadiazol-5-carbohydrazide III, to get the yellow solid after drying 0.87 g, yield 94.87% ; in order to 5-chloro -1, 2, 3-thiadiazol-4-carboxylic acid ethyl ester, 5-methyl -1, 2, 3-thiadiazol-4-carboxylic acid ethyl ester, 1, 2, 3-thiadiazol-4-carboxylic acid ethyl ester, 4-cyclopropyl -1, 2, 3-thiadiazol-5-carboxylic acid ethyl ester instead of 4-methyl -1, 2, 3-thiadiazol-5-carboxylic acid the ethyl ester may preparation of 5-chloro -1, 2, 3-thiadiazol-4-carbohydrazide, 5-methyl -1, 2, 3-thiadiazol-4-carbohydrazide, 1, 2, 3-thiadiazol-4-carbohydrazide, 4-cyclopropyl -1, 2, 3-thiadiazol-5-carbohydrazide.

References:

CN103641795,2016,B Location in patent:Paragraph 0057; 0058; 0059