作者:Mark A. Hempenius、Cees Erkelens、Patrick P. J. Mulder、Han Zuilhof、Wouter Heinen、Johan Lugtenburg、Jan Cornelisse
DOI:10.1021/jo00063a029
日期:1993.5
A study of the charge distribution in the 1-hydropyrenyl anion (2-), and 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 its 1-position fixed with a spirocyclopentane ring. Highly resolved H-1 and C-13 NMR spectra of this spiro[cyclopentane-1,1'-[1H]pyrenyl] anion (1-) and of 2- were obtained. These spectra could be completely assigned by means of COSY, NOESY, and 2D H-1-C-13 COSY techniques. According to the C-13 NMR measurements, 5-C of 1- and 2- bears the highest negative charge. The results of PM3 semiempirical calculations support this finding and, furthermore, a large HOMO coefficient was calculated at the quaternary 3a-C of 2-, suggesting that this position is susceptible 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 anion (2-) was assumed to be the most reactive position, and soft electrophiles were thought to attack 10a-C of 2-.