Synthesis of 3-Acyl-isoxazoles and Δ<sup>2</sup>-Isoxazolines from Methyl Ketones, Alkynes or Alkenes, and <i>tert</i>-Butyl Nitrite via a Csp<sup>3</sup>–H Radical Functionalization/Cycloaddition Cascade
A novel metal-free tandem Csp3–H bond functionalization of ketones and 1,3-dipolar cycloaddition has been developed. An efficient approach to a variety of oxazole and isoxazoline derivatives is demonstrated using the 1,3-dipolar cycloaddition of alkynes and alkenes to nitrile oxides generated by reactions of methylketones with tert-butyl nitrite. This new protocol provides access to a variety of isoxazolines
Copper Nitrate Mediated Regioselective [2+2+1] Cyclization of Alkynes with Alkenes: A Cascade Approach to Δ<sup>2</sup>-Isoxazolines
作者:Mingchun Gao、Yingying Li、Yuansheng Gan、Bin Xu
DOI:10.1002/anie.201503393
日期:2015.7.20
An efficient method for the regioselective synthesis of pharmacologically relevant polysubstituted Δ2‐isoxazolines is based on the copper‐mediated direct transformation of simple terminal alkynes and alkenes. The overall process involves the formation of four chemical bonds with inexpensive and readily available copper nitrate trihydrate as a novel precursor of nitrile oxides. The reaction can be easily