Sterically congested polycyclic aromatic hydrocarbons with nonoptimal geometries. 4,5-Didehydroacenaphthene as a precursor for the synthesis of 7,14-diphenyl-8,9-(1',8'-naphthenylene)acephenanthrene

A multistep synthetic route for the synthesis of the reactive intermediate 4,5-didehydroacenaphthene (15) is described. A mixture of N-1-, N-2-, and N-3-aminoacenaphtho [4,5-e] triazoles is produced, which is oxidized by lead tetraacetate (LTA) to the corresponding aryne. The N-2-triazole is oxidized by LTA to 7-cyano-1-(cyanomethylene) indan (18), whose structure was verified by X-ray analysis. Intermediate 15 was trapped by 7,9-diphenyl-8H-cyclopenta [a] acenaphthylen-8-one (acecyclone) to produce the congested hydrocarbon 7,14-diphenyl-8,9-(1',8'-naphthenylene) acephenanthrene (20). There is a small deviation from planarity for 20, and this is modeled by MMX calculations and verified by X-ray crystallographic analysis of the structure