Synthesis of Three Helically Chiral Iptycenes

Article abstract of DOI:10.1021/jo00024a038

The synthesis of iptycenes 2-4, each of which is helically chiral and has C₂ symmetry axis, is described.Key intermediates are diene 7, prepared in two step and 44percent yield from known ketone 5, and anthracene 11, prepared in four steps and 48percent yield from diene 7.A noteworthy step in the latter sequence is the aluminum chloride catalyzed, room-temperature, regio- and stereoselective cycloaddition of naphthoquinone 8 to diene 7 to give a single isomer of 9.Anthracene 11 was converted in one step to 2 and in four steps to 3 (Scheme II).Bicycloalkene 15, an intermediate in the latter synthesis, was converted to 4 in two steps (Scheme III).Cycloaddition of unactivated dienophile 15 to unactivated dienes 17 and 18 proceeds in good yields.Hydrocarbon 3 could be resolved on several chiral columns.