Microwave assisted regiospecific synthesis of 5-trifluoromethyl-4,5-dihydropyrazoles and—pyrazoles

✍ Scribed by Marcos A. P. Martins; Claudio M. P. Pereira; Sidnei Moura; Clarissa P. Frizzo; Paulo Beck; Nilo Zanatta; Helio G. Bonacorso; Alex F. C. Flores

• Publisher: Journal of Heterocyclic Chemistry
• Year: 2007
• Tongue: English
• Weight: 311 KB
• Volume: 44
• Category: Article
• ISSN: 0022-152X
• DOI: 10.1002/jhet.5570440537

✦ Synopsis

Abstract

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The regiospecific synthesis of a series of twelve 5‐trifluoromethyl‐4,5‐dihydropyrazoles and ‐pyrazoles from the cyclocondesation reaction of 4‐alkoxy‐1,1,1‐trifluoro‐3‐alken‐2‐ones [F~3~CC(O)CH=C(R^1^)OR, where R^1^ = Me, Et, Pr, iso‐Pr, Bu, iso‐Bu, Ph, H; and R = Me, Et] with phenylhydrazine in toluene by environmentally benign microwave induced techniques is reported. It is shown that under appropriated conditions, the variation of microwave irradiation power leads to 4,5‐dihydropyrazole or pyrazole derivatives. This paper also includes the use of montmorillonite K‐10 as a solid support for the synthesis of pyrazoles under solvent free conditions.