One-pot synthesis of 3(5)-ethoxycarbonylpyrazoles

A one-pot synthesis of ethoxycarbonylpyrazoles 2a-e, by the cyclocondensation of beta-alkoxyvinyl trichloromethyl ketones la-e with hydrazine hydrochloride under mild conditions, is reported. A study using compounds 1a-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 (70-91%).