Experimental NMR and DFT studies of persistent carbocations derived from hetero-polycyclic aromatic hydrocarbons containing oxygen atom: Dibenzo[b,d]furan, Benzo[b]naphtho[1,2-d]furan, Benzo[b]naphtho[2,3-d]furan, Benzo[b]naphtho[2,1-d]furan, and Dinaphtho[2,1-b: 1′,2′-d]furan
Document Type
Article
Publication Date
1-1-2014
Abstract
Persistent protonation carbocations generated from hetero-PAHs containing oxygen atoms in their aromatic rings, dibenzo[b,d]furan (5), benzo[b]naphtho[1,2-d]furan (6), benzo[b]naphtho[2,3-d]furan (7), benzo[b]naphtho[2,1-d]furan (8), and dinaphtho[2,1-b: 1′,2′-d]furan (9), were directly observed by NMR measurements in superacid. Compound 5 was protonated mainly at C(2) in FSO3H-SbF5 (1: 1) or (4: 1)/SO2ClF, and 6, 8, and 9 were protonated exclusively at C(5) in CF3SO3H or FSO3H/SO2ClF, whereas 7 was protonated at C(6) and C(11) to give two species in FSO3H/SO2ClF. Surprisingly, compound 5 resists protonation in FSO3H/SO2ClF to show NMR spectra corresponding to that of the intact material. Positive charge delocalization mapping for carbocations based on experimental Δδ13C values indicates limited delocalization in these systems. The chemical shifts and charge delocalization modes derived by DFT calculations agreed with the experimental results.
Publication Title
Bulletin of the Chemical Society of Japan
Volume
87
Issue
11
First Page
1235
Last Page
1244
Digital Object Identifier (DOI)
10.1246/bcsj.20140182
ISSN
00092673
E-ISSN
13480634
Citation Information
Okazaki, Nakagawa, M., Kitagawa, T., & Laali, K. K. (2014). Experimental NMR and DFT Studies of Persistent Carbocations Derived from Hetero-Polycyclic Aromatic Hydrocarbons Containing Oxygen Atom: Dibenzo[b,d]furan, Benzo[b]naphtho[1,2-d]furan, Benzo[b]naphtho[2,3-d]furan, Benzo[b]naphtho[2,1-d]furan, and Dinaphtho[2,1-b:1′,2′-d]furan. Bulletin of the Chemical Society of Japan, 87(11), 1235–1244. https://doi.org/10.1246/bcsj.20140182