A third-generation bicyclopropylidene: straightforward preparation of 15,15'-bis-(hexaspiro[18.104.22.168.0.0.2.0.22.214.171.124]pentadecylidene) and a C2v-symmetric branched triangulane.
The synthesis of highly strained branched triangulane I has been achieved by a copper assisted dimerization of 1-bromo-1-lithiocyclopropanes. 7,7-Dibromodispiro[126.96.36.199]heptane (II) underwent successive dimerization, cycloaddn., and dimerization to provide third generation bicyclopropylidene III. III proved resistant to cycloaddn. by dibromocarbenes but with less sterically demanding carbenes, e.g. dichlorocarbene, cycloaddn. occurred to give the corresponding dichlorocyclopropanes which underwent dehalogenation to produce I.
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