Synthesis of Pyrazoles via Electrophilic Cyclization

ZORA M., KIVRAK A., YAZICI C.

JOURNAL OF ORGANIC CHEMISTRY, vol.76, no.16, pp.6726-6742, 2011 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 76 Issue: 16
  • Publication Date: 2011
  • Doi Number: 10.1021/jo201119e
  • Journal Name: JOURNAL OF ORGANIC CHEMISTRY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.6726-6742
  • Middle East Technical University Affiliated: Yes

Abstract

Electrophilic cyclizations of alpha,beta-alkynic hydrazones by molecular iodine were investigated for the synthesis of 4-iodopyrazoles. alpha,beta-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, alpha,beta-alkynic hydrazones underwent electrophilic cyclization to afford 4-iodopyrazoles in good to high yields. Iodocyclization was general for a wide range of alpha,beta-alkynic hydrazones and tolerated the presence of aliphatic, aromatic, heteroaromatic, and ferrocenyl moieties with electron-withdrawing and electron-donating substituents.