Facile Access to Versatile Polyaromatic Building Blocks: Selectively Protected Benzocyclobutenedione Derivatives via Regioselective [2+2] Cycloaddition of α-Alkoxybenzyne and Ketene Silyl Acetal

A facile, divergent access to highly oxygenated benzocyclobutene derivatives was developed via the regioselective [2+2] cycloaddition of α-alkoxybenzynes and ketene silyl acetals. The cycloadducts could be converted to selectively protected alkoxybenzocyclobutenediones, an attractive class of compounds for the synthesis of polyaromatic compounds. As one possible application, divergent access to a regioisomer pair of sulfonylphthalides for the Hauser approach to polyaromatic compounds is described.