Mechanistic study of silica-gel or FeCl3-promoted ring-opening aromatization of 7-oxanorborna-2,5-dienes affording 2-bromo-3-hydroxybenzoate derivatives

摘要

One-pot synthesis of 2-bromo-3-hydroxybenzoates by the Diels-Alder reaction of furans with bromoalkyne and the subsequent ring-opening aromatization was studied by means of deuterium-labeling experiments. The residual protons in silica gel were considered to be the hydrogen source of the hydroxy group of products under the silica gel-promoted condition. The deuterium-labeling experiment revealed a rapid equilibrium among the intermediates prior to the aromatization under FeCl3-catalyzed condition.