title: Base-mediated reaction of hydrazones and nitroolefins with a reversed regioselectivity: a novel synthesis of 1,3,4-trisubstituted pyrazoles.
abstract: A regioselective synthesis of 1,3,4-tri- or 1,3,4,5-tetrasubstituted pyrazoles by the reaction of hydrazones with nitroolefins is described. Mediated with strong bases such as t-BuOK, the reaction exhibits a reversed, exclusive 1,3,4-regioselectivity. Subsequent quenching with strong acids such as TFA is essential to achieve good yields. A plausible stepwise cycloaddition reaction mechanism is proposed.
authors.affiliation: Johnson & Johnson Pharmaceutical Research & Development, L.L.C., 3210 Merryfield Row, San Diego, California 92121, USA. xdeng@prdus.jnj.com
authors.forename: Xiaohu
authors.initials: X
authors.lastname: Deng
authors.forename: Neelakandha S
authors.initials: NS
authors.lastname: Mani
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D006835:Hydrazones / Q000737:chemistry*; D017672:Nitrogen Compounds / Q000737:chemistry*; D011720:Pyrazoles / Q000138:chemical synthesis*
chemical_list: D000475:Alkenes; D006835:Hydrazones; D017672:Nitrogen Compounds; D011720:Pyrazoles