One-Pot Tandem Synthesis of Tetrasubstituted Pyrazoles via 1,3-Dipolar Cycloaddition Between Aryl Hydrazones and Ethyl But-2-ynoate
摘要:
1,3,4,5-Tetrasubstituted pyrazoles are rapidly and regioselectively synthesized in a one-pot, three-step sequence consisting of condensation, nitrilimine generation, and cycloaddition using mercuric acetate. Newly synthesized compounds were characterized by spectral studies. Regiochemistry of compounds 6a and 8a was determined as 1,4- and 1,5-regioisomers respectively by X-ray crystallography.
A variety of fully substituted pyrazoles were easily prepared through a three-component condensation of aldehydes, arylhydrazines, and ethyl acetoacetate in the presence of catalytic amounts of zinc triflate [Zn(OTf)2] under solvent-free conditions. Selective synthesis of symmetrical and unsymmetrical bispyrazoles from dialdehydes in high yields can be considered as a notable advantage of this method.
An efficient, rapid, and green synthesis of functionalized pyrazoles has been accomplished under solvent-freeconditions by the reaction of phenyl hydrazine, aldehydes and ethyl acetoacetate. This approach exploits the synthetic potential of microwave irradiation and scandium triflate combination and offers many advantages such as excellent product yields, shorter reaction time, easy isolation of products
Silica chloride catalyzed one-pot synthesis of fully substituted pyrazoles
作者:Dhanaji V. Jawale、Umesh R. Pratap、Jyotirling R. Mali、Ramrao A. Mane
DOI:10.1016/j.cclet.2011.05.016
日期:2011.7
Silica chloride catalysted one pot cyclocondensation of aldehydes, ethyl acetoacetate and phenyl hydrazine leading to substituted pyrazoles has been reported. (C) 2011 Ramrao A. Mane. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.