One-pot synthesis of aryl and heteroaroyl-substituted hydroxypyrazolines from the reactions of β-alkoxyvinyl trichloromethyl ketones with heteroarylhydrazides

The one-step regiospecific synthesis of a novel series of 10 trichloromethyl-, aryl, and heteroaroyl-substituted 5-hydroxy-2-pyrazolines affords 142-thenoyl)-, 1-(2-furoyl)-, and 1-(isonicotinoyl)-3-aryl-5-hydroxy-5-trichloromethyl-4,5-dihydro-1H- pyrazoles in 63-92% yields from the cyclocondensation reactions of 1,1,1-trichloro-4-methoxy-4aryl-3-buten-2-ones (where aryl substituents are -C6H5, 4-CH3C6H4, 4-OCH3C6H4, 4-FC6H4, 4-ClC6H4, 4-BrC6H4) with 2-thiophenecarboxylic hydrazide, furoic hydrazide, and isonicotinic acid hydrazide, respectively. Dehydration reaction of two 2-pyrazolines with P2O5 furnished the corresponding 1H-pyrazoles in low yields (21-29%). (c) 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:685-691, 2006; Published online in Wiley InterScience (www.interscience.wiley.com).