Phenylenes with Mixed Topology the Bent Isomers

S Phenylenes with Mixed Topology the Bent Isomers 

The synthesis of anti-doublebent [5]phenylene 56 [74] commenced with the tet-rahalogenated C2h-symmetric 53 [75]. Another use of the versatile building block 23 provided 54. Subsequent coupling with TMSA and deprotection afforded 55. The cyclization initially failed when attempted with [CpCo(CO)2] as the catalyst, but was later rendered successful by the application of the milder [CpCo(eth)2] conditions [74]. 

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