An Oxygen-peri-Bridged Quinolinium Cation and Its Monoradical Counterpart

作者：Kotha Raghavendhar R; Nash John J; Kenttaemaa Hilkka I^*

来源：European Journal of Organic Chemistry, 2017, 2017(11): 1407-1412.

DOI：10.1002/ejoc.201601572

• Diradicals
• Gas-phase reactions
• Mass spectrometry
• Monoradicals
• Radical ions
• Radical reactions
• Reaction mechanisms
• Reactive intermediates

Generation of a sigma, sigma, pi-triradical was attempted by collision-activated dissociation (CAD) of two iodine atoms and an NO- radical from 2,4-diiodo-5-nitroquinolinium cation in an ion trap mass spectrometer. However, the reactivity of the product was consistent with a monoradical rather than a triradical. The mechanism of its formation was explored. In the first CAD step, an iodine atom is lost to generate the 2-iodo-5-nitro-4-dehydroquinolinium cation. Quantum chemical calculations suggest that in the second CAD step, the radical site at C-4 adds to the adjacent NO2 group followed by loss of NO- to generate the 2-iodo-4-oxyl-5-dehydroquinolinium cation. Calculations also suggest that in the third CAD step, this cation cyclizes to form an oxygen-peri-bridged 2-iodoquinolinium cation that then loses the remaining iodine atom to generate a distonic 4,5-oxygen-peri-bridged 2-dehydroquinolinium cation. For the analogous 4-oxyl-5-dehydroquinolinium cation, the cyclization is calculated to be exoergic by 8.7 kcal mol(-1), with a free energy barrier of 14.0 kcal mol(-1). The cyclized product is the first experimentally observed oxygen-peri-bridged naphthalene derivative. It displays low reactivity. However, it's monoradical counterpart is highly reactive and undergoes typical radical reactions.

• 出版日期2017-3-17