An Elusive Nonaromatic Goal behind the Centropolyindanes: Aufbau of Veratrolo-Annelated Centropolyquinanes and Ozonolytic Abbau.

This study presents a potential experimental approach to the still elusive topologically nonplanar (K5 ) parent hydrocarbon, centrohexaquinane (1), by a construction-dismantling (aufbau-abbau) strategy via electron-rich aromatic centropolyindanes. A series of veratrole-based centropolyindanes are synthesized and subjected to ozonolytic degradation. These include the 2,2'-spirobiindanes 30-32, fuso-diindane 33, triptindanes 34-36, tribenzotriquinacene 37, and tetramethoxycentrohexaindane 9. Spirane 30 and propellane 36 are characterized by X-ray structure analysis. Ozonolysis of 32 and 33 gives a keto ester (59) and a dimethyl muconate (60), respectively. Dimethoxytriptindane 34 gives a [3.3.3]propellane-cis,cis-muconate (61) in good yield, the stereochemistry of which is determined by X-ray structure analysis. Tetramethoxytriptindane 35 gives the [3.3.3]propellane-bis-muconate 62 along with a [3.3.3]propellane-dialdehyde-muconate (63). Hexamethoxytriptindane 36 furnishes three products of mainly intra-dimethoxy cleavage, with the [3.3.3]propellane-tris-muconate 64 as the major component. X-ray structure analysis of 64 reveals molecular C3 symmetry and all-cis,cis stereochemistry of the three muconate groups. Hexamethoxytribenzotriquinacene 37 gives the triquinacene-tris-muconate 68, albeit in very low yield. Ozonolysis of tetramethoxycentrohexaindane 9 affords the bis-muconate 10 in moderate yield, along with two further centrohexacyclic products of single-wing degradation.