Copper-Catalyzed Cascade Annulation of o-Hydroxyphenyl Propargylamines with Pyrazolin-5-ones to Access Pyrano[2,3- c]pyrazoles

J Org Chem. 2022 May 6;87(9):5795-5803. doi: 10.1021/acs.joc.2c00122. Epub 2022 Apr 20.

Abstract

An efficient copper-catalyzed cascade annulation of o-hydroxyphenyl propargylamines and pyrazolin-5-ones is described. This methodology leads to the rapid assembly of a series of valuable pyrano[2,3-c]pyrazoles with good yields across a wide range of substrates in a simple fashion. This novel reaction involves the formation of alkynyl ortho-quinone methides, a 1,4-conjugate addition, and a subsequent 6-endo cyclization process. The mechanistic elucidation is well supported by control experiment and literature precedents.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Catalysis
  • Copper
  • Pargyline / analogs & derivatives
  • Propylamines
  • Pyrazoles
  • Pyrazolones*

Substances

  • Propylamines
  • Pyrazoles
  • Pyrazolones
  • propargylamine
  • Copper
  • Pargyline