T. Ueno, H. Toda, M. Yasunami
Jun 15, 1996
Citations
0
Influential Citations
27
Citations
Journal
Bulletin of the Chemical Society of Japan
Abstract
1-Fluoro- and 1,3-difluoroazulenes were synthesized for the first time by the electrophilic fluorination of azulenes with N-fluoro reagents. Selective preparation of 1-fluoroazulenes were performed by the fluorination of methyl azulene-1-carboxylates, followed by demethoxycarbonylation in 100% H3PO4. 2-Substituted azulenes were fluorinated in higher yields. In the 1H NMR of 1-fluoroazulene, long-range JFH values were not observed at H-2 and H-8, in contrast to those for 1-fluoronaphthalene. The 1-fluorine atom causes significant bathochromic shifts in the visible absorption of azulene, due to the so-called +Iπ effect.