title: Regioselective synthesis of 1,3,5-tri- and 1,3,4,5-tetrasubstituted pyrazoles from N-arylhydrazones and nitroolefins.
abstract: Two general protocols are developed for the regioselective synthesis of 1,3,5-tri- and 1,3,4,5-tetrasubstituted pyrazoles by the reaction of electron-deficient N-arylhydrazones with nitroolefins. Studies on the stereochemistry of the key pyrazolidine intermediate suggest a stepwise cycloaddition mechanism.
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*; D003500:Cyclization; D006835:Hydrazones / Q000737:chemistry*; D009574:Nitro Compounds / Q000737:chemistry*; D011720:Pyrazoles / Q000138:chemical synthesis*
chemical_list: D000475:Alkenes; D006835:Hydrazones; D009574:Nitro Compounds; D011720:Pyrazoles