Synthesis of 1H-Cyclopent[cd]indene and its Anion

In connection with studies of 2H-benz[cd]azulene (1) [¹] and the strongly acidic fluoradene (2) [²] particular interest[²⁻⁶] attaches to the parent system of the latter, 2aHcyclopent[cd]indene (3) and its 1 H-isomer (4) as well as to their anion (5) which is isoelectronic with [3.2.2]cy-clazine (6)[³].