An Environmentally Benign Multicomponent Cascade Reaction of 3-Formylchromones, 2-Naphthols, and Heterocyclic Ketal Aminals: Site-Selective Synthesis of Functionalized Morphan Derivatives

J Org Chem. 2022 Jul 1;87(13):8562-8575. doi: 10.1021/acs.joc.2c00695. Epub 2022 Jun 14.

Abstract

A novel protocol has been developed for the preparation of highly functionalized 2-azabicyclo[3.3.1]nonane (morphan) derivatives by the interesting three-component cascade reaction of 3-formylchromones, 2-naphthol, and heterocyclic ketal aminals (HKAs) in the ionic liquid [BMIM]PF6 promoted by the organic base Et3N. A complex cascade reaction is required, which includes a 1,2-addition, two Michael reactions, two tautomerizations, and an N-alkylation accompanied by a ring-opening reaction and involving the cleavage of one C-O bond and the formation of four bonds (one C-N bond, one C-O bond, and two C-C bonds). As a result, functionalized morphans (5 and 6) bearing naphthalene-structured skeletons were prepared by simple heating of a mixture of 3-formylchromones, 2-naphthols, and HKAs in the environmentally friendly ionic liquid [BMIM]PF6. This protocol can be used in the synthesis of various morphans and is suitable for combinatorial and parallel syntheses of natural-like morphan derivatives. This approach has several advantages such as the use of an environmentally friendly solvent, simple and practical operation (multicomponent one-pot reaction), and satisfactory yields (65-88%).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromones
  • Ethers
  • Ionic Liquids* / chemistry
  • Naphthols*
  • Solvents / chemistry

Substances

  • Chromones
  • Ethers
  • Ionic Liquids
  • Naphthols
  • Solvents
  • formylchromone
  • 2-naphthol