3-Formylchromones IV. The rearrangement of 3-formylchromone enamines as a simple, facile route to novel pyrazolo[3,4-b]pyridines and the synthetic utility of the latter

Molecules. 2005 Aug 31;10(7):809-21. doi: 10.3390/10070809.

Abstract

One-pot and facile preparations of 6-(2-hydroxy-5-R-benzoyl)-4-methyl-2-R1- pyrazolo[3,4-b]pyridines 4a-o are described, using the reaction of 3-formyl chromones 1 with 5-amino-1-R1-pyrazoles 2. An enamine-intermediate 2-ethyloxy-6-R-3-(3-methyl-1- phenylpyrazol-5-ylaminomethylene)chroman-4-one 3 was isolated at lower temperatures. Acyloxy-derivatives 5 of compounds 4 were obtained by acylation with acid chlorides or acid anhydrides. Coumarins 6 substituted at the 3- and 4-positions were prepared from the pyrazolo[3,4-b]pyridines 4 by condensation reactions and hydrazones 7 were formed from their reaction with 2,4-dinitrophenyl hydrazine. Reactions under microwave irradiation proceeded significantly faster and with high yields.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amines / chemistry
  • Chromogranins / chemistry*
  • Chromogranins / pharmacology
  • Chromones / chemistry*
  • Coumarins
  • Microbial Sensitivity Tests
  • Pyrazoles / chemical synthesis*
  • Pyrazoles / pharmacology
  • Pyridines / chemical synthesis*
  • Pyridines / pharmacology
  • Pyrimidines / chemical synthesis*
  • Pyrimidines / pharmacology

Substances

  • Amines
  • Chromogranins
  • Chromones
  • Coumarins
  • Pyrazoles
  • Pyridines
  • Pyrimidines
  • formylchromone
  • coumarin