HIGHLY REGIOSELECTIVE SYNTHESIS OF 1-ACYL-5-HYDROXYPYRAZOLINES OR SYNTHESIS OF 3,5-DISUBSTITUTED PYRAZOLES FROM (E)-beta-CHLOROVINYL KETONES AND BENZOHYDRAZIDES OR HYDRAZINE HYDRATE

摘要

Highly regioselective synthesis of 1-acyl-5-hydroxypyrazolines or synthesis of 3,5-disubstituted pyrazoles have been achieved through the cyclocondensation of (E)/beta-chlorovinyl ketones with benzohydrazides/hydrazine hydrate under extremely mild reaction conditions. The mechanistic studies showed that diverse electrophilic pathways of (E)-beta-chlorovinyl ketones could be observed by using different nucelophilic species. Moreover, the utility of the tandem reaction is further illustrated by the concise synthesis of 1-acyl-pyrazole and 3-pentyl-5-phenyl-1H-pyrazole.