The synthesis of iptycenes 2-4, each of which is helically chiral and has a C2 symmetry axis, is described. Key intermediates are diene 7, prepared in two steps and 44% yield from known ketone 5, and anthracene 11, prepared in four steps and 48% 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.
The synthesis of iptycenes 2-4, each of which is helically chiral and has a C2 symmetry axis, is described. Key intermediates are diene 7, prepared in two steps and 44% yield from known ketone 5, and anthracene 11, prepared in four steps and 48% 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.
The synthesis of iptycenes 2-4, each of which is helically chiral and has a C2 symmetry axis, is described. Key intermediates are diene 7, prepared in two steps and 44% yield from known ketone 5, and anthracene 11, prepared in four steps and 48% 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.