The synthesis of benz-, naphth-, and anth-annelated dihydropyrenes as aids to measuring aromaticity by NMR

Benzo[e]-, naphtho[e]- and anthro[e]-fused 2,7-di-t-butyl-trans-10b,10c-dimethyldihydropyrenes are synthesized via an ‘aryne–furan’ Diels–Alder reaction and the series used to establish a relative aromaticity scale for estimating resonance energies (bond localization energies) using NMR chemical shift data of the internal methyl protons of the dihydropyrenes.