The Friedel-Crafts acetylation of 5-hydroxyindole derivativesla-c regioselectively produced 6-acetyl-5-hydroxy-indole derivatives2a-c which were condensed with cinnamic acid using POC13 and dry pyridine to afford 5-cinnamoyloxy-6-acetyl-indoles3a-c. These upon Baker-Venkataraman transformation furnished 6-cinnamoylacetyl-5-hydroxyindoles4a-c which were cyclised separately with AcOH/HCl and Ac2O/AcONa to 4H-pyrano-(2,3-f)indol-4-one derivatives5a-c and6a-c respectively.
Volume 134, 2022
Continuous Article Publishing mode
Click here for Editorial Note on CAP Mode