Reaction of N-methyl-5-tributylstannyl-4-fluoro-1H-pyrazole and its application to N-methyl-chromeno[2,3-d]pyrazol-9-one synthesis.
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.
Hanamoto
Takeshi
T
Department of Chemistry and Applied Chemistry, Saga University, Saga, Japan. hanamoto@cc.saga-u.ac.jp
Hashimoto
Eri
E
Miura
Masayuki
M
Furuno
Hiroshi
H
Inanaga
Junji
J
D009682:Magnetic Resonance Spectroscopy; D011720:Pyrazoles / Q000138:chemical synthesis* / Q000737:chemistry
D011720:Pyrazoles