Indanones and Indenols from2-Alkylcinnamaldehydes via the IntramolecularFriedel-Crafts Reaction of Geminal Diacetates

摘要

When treated with Ac_20 at rt in the presence of 4-6 mol %FeCl_3, 2-alkylcinnamaldehydes are converted to 2-alkyl-1H-inden- 1 -yl acetates through the intermediacy of gem-diacetates. Methanolysis of the indenyl acetates yields thecorresponding indenols. Saponification yields 2-alkylinda-nones, providing, in effect, an intramolecular acylationemploying catalytic levels of acid.