16021-60-6Relevant articles and documents
Computational assessment of the electronic structure of 1-azacyclohexa-2,3,5-triene (3δ2-1H-pyridine) and its benzo derivative (3δ2-1H-quinoline) as well as generation and interception of 1-methyl-3δ2-1H-quinoline
Schoeneboom, Jan C.,Groetsch, Stefan,Christl, Manfred,Engels, Bernd
, p. 4641 - 4649 (2003)
Treatment of a solution of 3-bromo-1-methyl-1,2-dihydroquinoline (9) and [18]crown-6 in furan or styrene with KOtBu followed by hydrolysis afforded a mixture of 1-methyl-1,2-dihydroquinoline (10) and 1-methyl-2-quinolone (11). If the reaction was performed in [D8]THF and the mixture was immediately analysed by NMR spectroscopy, 2-tert-butoxy-1-methyl-1,2-dihydroquinoline (17) was shown to be the precursor of 10 and 11. The structure of 17 is evidence for the title cycloallene 7, which arises from 9 by β elimination of hydrogen bromide and is trapped by KOtBu to give 17 so fast that cyclo-additions of 7 with furan or styrene cannot compete. Since this reactivity is unusual compared to the large majority of the known six-membered cyclic allenes, we performed quantum-chemical calculations on 8, which is the parent compound of 7, and the corresponding isopyridine 6 to assess the electronic nature of these species. The ground state of 6 was no longer an allene (6a) but the zwitterion 6b. In the case of 8, the allene structure 8a is more stable than the zwitterionic form 8b by only ≈1 kcal mol-1. These results suggest a high reactivity of 6 and 8 towards nucleophiles and explains the behaviour of 7. In addition to the ground states, the low-lying excited states of 6 and 8 were considered, which are represented by the diradicals 6c and 8c and, as singlets, lie above 6b and 8a by 19.1 - 24. 8 and 14.4-17.7 kcal mol-1, respectively.
Non-electronic aromatic ring activation by simple steric repulsion between substituents in 1-methylquinolinium salt systems
Iwai, Kento,Yokoyama, Soichi,Asahara, Haruyasu,Nishiwaki, Nagatoshi
, p. 50 - 57 (2020)
A systematic study of non-electronic activation of an aromatic ring was performed using a series of 8-substituted 1-methylquinolinium salts. As the 8-substituent became bulkier, the quinoline framework was distorted by steric repulsion between substituents at the 1- A nd 8-positions. This was accompanied by lack of coplanarity, which brought about dearomatization. Consequently, quinolinium ions possessing a bulky 8-substituent exhibited high reactivity undergoing nucleophilic addition at the 2-position efficiently. We demonstrate that the activation was achieved sterically and not electronically.
Regioselective Reduction of 1-Methylquinolinium lons by Tributyltin Hydride and Tris(trimethylsilyl)silane via Photoinduced Electron Transfer
Fukuzumi, Shunichi,Noura, Souta
, p. 287 - 288 (2007/10/02)
Thermal reduction of 1-methylquinolinium ion by tributyltin hydride occurs via a polar mechanism to yield 1-methyl-1,2-dihydroquinoline selectively, while the photoreduction of 1-methylquinolinium ion derivatives by tributyltin hydride and tris(trimethylsilyl)silane proceeds via photoinduced electron transfer from the metal hydrides to the singlet excited states of 1-methylquinolinium ion derivatives to yield the corresponding 1,4-dihydroquinolines exclusively.
