Synthesis of Singly and Doubly Cage‐Annulated Bicyclo[2.2.2]octenes Derived from Triptycene Skeleton

Abstract

AbstractTriptycene‐diquinone 5 was synthesized from 1,4‐dimethoxyanthraene (6b) and found to undergo Diels‐Alder reaction with 5,5‐dimethoxy‐1,2,3,4‐tetrachlorocyclopentadiene (DTCp) to afford exclusively the least symmetric (Cs) bis‐adduct 4b. The double Diels‐Alder reaction exhibited π‐facial selectivity, in which the initial cycloaddition occurred preferentially on the π‐face of the benzoquinone moiety of 5 that is syn to the other benzoquinone unit (about 6:1), thereby producing the corresponding mono‐adducts 13b and 13a. Both stereoisomeric 13a and 13b underwent the second cycloaddition via exclusively the π‐face that is opposite to the orientation of previous DTCp addition 5, thus leading to the formation of bis‐adduct 4b as sole product. The structure of 4b was unequivocally established by X‐ray structural determination.