title: Reaction of N-methyl-5-tributylstannyl-4-fluoro-1H-pyrazole and its application to N-methyl-chromeno[2,3-d]pyrazol-9-one synthesis.
abstract: N-Methylation by sequential treatment of 5-tributylstannyl-4-fluoro-1H-pyrazole 1 with LDA and iodomethane regioselectively afforded the compound 2a in high yield. The addition reaction of 5-lithiated-4-fluoro-1H-pyrazole generated from 2a with a wide range of electrophiles allowed a facile introduction of different substituents at position 5 in good yields. The adduct 3d was efficiently converted to N-methyl-chromeno[2,3-d]pyrazol-9-one 9 in 3 steps.
authors.affiliation: Department of Chemistry and Applied Chemistry, Saga University, Saga, Japan. hanamoto@cc.saga-u.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hanamoto
authors.forename: Eri
authors.initials: E
authors.lastname: Hashimoto
authors.forename: Masayuki
authors.initials: M
authors.lastname: Miura
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Furuno
authors.forename: Junji
authors.initials: J
authors.lastname: Inanaga
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D011720:Pyrazoles / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D011720:Pyrazoles