Benzene and pyrene can be synthetically linked to [o-COSAN]- keeping their aromaticity. At difference, naphthalene and anthracene are extruded in the same reaction. We have proven that extrusion is only favorable if the number of Clar’s π-sextets remains constant. Thus, Clar has the answer to whether an attached polycyclic aromatic hydrocarbon to [o-COSAN]- is extruded or not.
Experimental studies were done by the group of Profs. Francesc Teixidor and Clara Viñas at Institute of Materials Science of Barcelona (ICMAB-CSIC) and calculations were performed in the IQTCUB institute by Prof. Jordi Poater and in the DiMoCat group of the IQCC by Prof. Miquel Solà.

The study was recently published in Angewandte Chemie International Edition:

J. Poater, C. Viñas, D. Olid, M. Solà, and F. Teixidor
“Aromaticity and Extrusion of Benzenoids Linked to [o-COSAN]-. Clar has the Answer”
Angew. Chem. Int. Ed. 2022, ASAP, DOI: 10.1002/anie.202200672