Bicyclisch verbruckte Cyclopentadienylanionen: 4,8-Etheno-/Ethano-2,4,6,8-tetrahydro-s-indacen-dianion

Two cyclopentadienes have been linked in a stereochemically rigid arrangement such that the cyclopentadienes are not coplanar. The key intermediates in the synthesis were tetrakis(methylene)bicyclo[2.2.2.]oct-2-ene (12) or -octane (14). The access to 12 and 14 was investigated in a comparative study including nine different precursors which were expected to lead to the methylene groups by elimination of HX. The best results were obtained with X=mesylate with overall yields of 52% for 12 in three steps and 42% for 14 in four steps