SPECTROMETRY AND REACTIVITY OF THE 1-HYDROPYRENYL ANION

A study of the charge distribution in the 1-hydropyrenyl anion (2-), a nd of its regioselectivity toward electrophilic attack was undertaken. In order to obtain reliable information on the reactive positions in 2-, a model with the same conjugated system was prepared, which has it s 1-position fixed with a spirocyclopentane ring. Highly resolved H-1 and C-13 NMR spectra of this spiro[cyclopentane-1,1'-[1H]pyrenyl] anio n (1-) and of 2- were obtained. These spectra could be completely assi gned by means of COSY, NOESY, and 2D H-1-C-13 COSY techniques. Accordi ng to the C-13 NMR measurements, 5-C of 1- and 2- bears the highest ne gative charge. The results of PM3 semiempirical calculations support t his finding and, furthermore, a large HOMO coefficient was calculated at the quaternary 3a-C of 2-, suggesting that this position is suscept ible toward attack by soft electrophiles. In full agreement with the C -13 NMR and PM3 results, 5-C of 1- and 2- show the highest reactivity toward electrophilic attack, while the quaternary 3a-C of 1- and 2- is attacked by soft electrophiles. These new results contradict earlier findings because until now, carbon atom 9-C of the 1-hydropyrenyl anio n (2-) was assumed to be the most reactive position, and soft electrop hiles were thought to attack 10a-C of 2-.