Zhang Zhong-tao
2011
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Journal
Fine chemicals
Abstract
2,3-Dichloropyridine was synthesized from 3-aminopyridine by substitution and diazotization,and then reacted with hydrazine to give 3-chloro-2-hydrazinopyridine by electrophilic substitution.The resultant can be used in the subsequent reaction without purification.Under the protection of nitrogen,with absolute ethanol as solvent,ethyl 3-chloro-2-hydrazinopyridine reacted with diethyl maleate to give 2-(3-chloro-2-pyridinyl)-5-oxo-3-pyrazolidinecarboxylate,the total yield of which was 48.0%.The structure of the products was confirmed by means of IR and 1HNMR.The synthesis process was optimized,and the optimum reaction conditions were ascertained as follows(based on 228.57 mmol of 3-chloro-2-hydrazinopyridine):in the reaction system with no water or oxygen,the speed of dropping diethyl maleate was 10 s/drop,the reflux was 1 h,and the yield was 80.1%.