Poly-Oxygenated Tricyclobutabenzenes via Repeated [2 + 2] Cycloaddition of Benzyne and Ketene Silyl Acetal

Described herein is a synthesis of highly functionalized tricyclobutabenzenes, a class of molecules of structural and theoretical interest. The preparation is based on the repeated [2 + 2] cycloadditions of benzyne and ketene silyl acetals (KSAs), where two types of regioselectivity enable discrimination of the functionalities on the four-membered rings. By these steps, we were able to prepare poly-oxygenated octamethoxytricyclobutabenzene and its hydrolyzed tetra-oxo derivatives. Structural study on the latter compound showed the interesting properties related to the strained four-membered ring.