BOND FIXATION IN A [14]ANNULENE - SYNTHESIS, CHARACTERIZATION, AND AB-INITIO COMPUTATIONS OF FURAN ADDUCTS DIMETHYLDIHYDROPYRENE

Furan adducts, 13, 15, and 16, of dimethyldihydropyrene are prepared i n order to test the postulate that bicyclic annelations are generally effective at inducing bond localization in aromatic systems. A large 2 -ppm down-field shift of the H-1 NMR shifts of the internal methyl sig nals in 15 compared to 16 provides a significant indicator of bond loc alization in 15. X-ray diffraction analysis of 13 displays regular bon d length alternation. Ab initio computations that do not include dynam ic electron correlation are found to be inadequate for modeling the mo lecular structure of 1. Density Functional Theory models 1 well and pr edicts bond localization in derivatives of 1 consistent with the obser ved NMR spectroscopic and X-ray diffraction results.