Haloacetylated enol ethers. 11 [16]. Synthesis of 1-methyl- and 1- phenyl pyrazole-3(5)-ethyl esters. A one-pot procedure

Article abstract of DOI:10.1002/jhet.5570360133

A one-pot synthesis of 1-methyl- and 1-phenylpyrazole-3(5)-ethyl esters 2,3a-e by the cyclocondensation of β-alkoxyvinyl trichloromethyl ketones 1a- e with methyl and phenyl hydrazine hydrochloride under mild conditions, is reported. A study using compounds la-e with different substituents proved that these are versatile building blocks for the synthesis of pyrazole derivatives, having a 3(5)-ethoxycarbonyl substituent in good yields (60- 89%). The hydrazine and β-alkoxyvinyl trichloromethyl ketone substituent effects on the reaction regiochemistry on the formation of the 1,3- and 1,5- isomer were observed.