A Divergent Synthesis of Dihydropyridazinones, N-Substituted Dihydropyrazoles, and O-Substituted Pyrazoles

作者：Masumoto Eiichi; Maruoka Hiroshi^*; Okabe Fumi; Nishida Sho; Yoshimura Yuki; Fujioka Toshihiro; Yamagata Kenji

来源：Journal of Heterocyclic Chemistry, 2011, 48(1): 96-104.

DOI：10.1002/jhet.519

Dihydropyridazinones 4a,b, N-substituted dihydropyrazoles 5b-d, and O-substituted pyrazoles 6a-d have been synthesized starting from spirocyclopropanepyrazole derivative 2. Treatment of 2 with alpha-chloro esters, e.g., methyl chloroacetate, ethyl chloroacetate, isopropyl chloroacetate, and tert-butyl chloroacetate, in potassium carbonate/sodium iodide system caused ring opening and subsequent C- or N-attack nucleophilic substitution to give the corresponding dihydropyridazinones 4a,b and N-substituted dihydropyrazoles 5b-d. On the other hand, in the absence of sodium iodide, O-substituted pyrazoles 6a-d were obtained from 2 via an O-attack nucleophilic substitution.

• 出版日期2011-1