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.
Regioreversed thermal and photochemical reduction of 10-methylacridinium and 1-methylquinolinium ions by organosilanes and oraganostannanes
Fukuzumi,Fujita,Noura,Ohkubo,Suenobu,Araki,Ito
, p. 1857 - 1868 (2007/10/03)
Irradiation of the absorption band of the 10-methylacridinium ion (AcrH+) in acetonitrile containing allylic silanes and stannanes results in the efficient and selective reduction of the 10-methylacridinium ion to yield the allylated dihydroacridines. In the photochemical reactions of AcrH+ with unsymmetric allylsilanes, the allylic groups are introduced selectively at the α position. Likewise, the reactions with unsymmetric allylstannanes afforded the α adducts predominantly, but the γ adducts were also obtained as minor products. In contrast to this, the thermal reduction of AcrH+ and the 1-methylquinolinium ion (QuH+) by unsymmetric allylstannanes gave only the γ adducts. The thermal reduction of QuH+ by tributyltin hydride or hydrosilanes in the presence of a fluoride anion also occurs to yield 1-methyl-1,2-dihydroquinoline selectively. On the other hand, the photoreduction of QuH+ derivatives by tributyltin hydride and tris(trimethylsilyl)silane yields the corresponding 1,4-dihydroquinolines exclusively. The difference in the mechanisms for the regioreversed thermal and photochemical reduction of AcrH+ and QuH+ is discussed in terms of nucleophilic vs electron-transfer pathways. The photochemical reactions proceed via photoinduced electron transfer from organosilanes and organostannanes to the singlet excited states of AcrH+ and QuH+, followed by the radical coupling of the resulting radical pair in competition with the back electron transfer to the ground state. The rate constants of photoinduced electron transfer obtained from the fluorescence quenching of AcrH+ and QuH+ by organosilane and organostannane donors agree with those obtained from the dependence of the quantum yields on the donor concentrations for the photochemical reactions. The electron-transfer rate constants are well analyzed in light of the Marcus theory of adiabatic outer-sphere electron transfer, leading to the evaluation of the reorganization energy (λ = 0.90 eV) of the electron-transfer reactions. The transient spectra of the radical pair produced by the photoinduced electron transfer from organosilanes to the singlet excited state of AcrH+ have been successfully detected in laser-flash photolysis of the AcrH+-organosilane systems. The rate constants of back electron transfer to the ground state have been determined, leading to the evaluation of the reorganization energy for the back electron transfer, which agrees with the value for the forward electron transfer.
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.
A Convenient Preparation of N-Acyl-1,2-dihydroquinoline
Katayama, Hajime,Ohkoshi, Mitsuko,Yasue, Masaiti
, p. 2226 - 2228 (2007/10/02)
N-Acetyl- and N-formyl-1,2-dihydroquinolone were conviniently prepared by reductive acylation of quinoline without isolating the labile 1,2-dihydroquinoline.This method was also applied to isoquinoline to prepare N-acetyl-1,2-dihydroisoquinoline.
