STUDIES OF THE SELECTIVE O-ALKYLATION AND DEALKYLATION OF FLAVONOIDS .16. DEMETHYLATION OF 2'-METHOXYACETOPHENONES WITH ANHYDROUS ALUMINUM-CHLORIDE OR BROMIDE IN ACETONITRILE

Demethylation of 2'-methoxyacetophenones with anhydrous aluminum chlor ide in acetonitrile was studied to survey its scope and limitations. T he mechanism which the reaction proceeds via sterically constrained in termediates was proposed from the substituent effects. Additionally, d ealkylation of 2'-benzyloxy-, 2'-ethoxy-, and 2'-isopropoxyacetophenon es with two demethylating reagents, hydrochloric acid in acetic acid a nd anhydrous aluminum bromide in acetonitrile, was studied. It was fou nd that the reactivity was greatly affected by the steric factor betwe en the alkoxyl group and reagent. This behavior may have wide applicat ion in selection of protecting groups in organic synthesis.