title: Synthesis of pyrazoles via electrophilic cyclization.
abstract: Electrophilic cyclizations of α,β-alkynic hydrazones by molecular iodine were investigated for the synthesis of 4-iodopyrazoles. α,β-Alkynic hydrazones were readily prepared by the reactions of hydrazines with propargyl aldehydes and ketones. When treated with molecular iodine in the presence of sodium bicarbonate, α,β-alkynic hydrazones underwent electrophilic cyclization to afford 4-iodopyrazoles in good to high yields. Iodocyclization was general for a wide range of α,β-alkynic hydrazones and tolerated the presence of aliphatic, aromatic, heteroaromatic, and ferrocenyl moieties with electron-withdrawing and electron-donating substituents.
authors: Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey. zora@metu.edu.tr
authors: Metin
authors: M
authors: Zora
authors: Arif
authors: A
authors: Kivrak
authors: Ceyda
authors: C
authors: Yazici
mesh_terms: D003500:Cyclization; D004583:Electrons; D005296:Ferrous Compounds / Q000737:chemistry; D006835:Hydrazones / Q000737:chemistry*; D007455:Iodine / Q000737:chemistry*; D015394:Molecular Structure; D011720:Pyrazoles / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D005296:Ferrous Compounds; D006835:Hydrazones; D011720:Pyrazoles; C010201:4-iodopyrazole; D007455:Iodine