491-34-9Relevant articles and documents
Iron-Catalysed Direct Aromatic Amination with N-Chloroamines
Douglas, Gayle E.,Raw, Steven A.,Marsden, Stephen P.
, p. 5508 - 5514 (2019)
An optimized procedure for the direct intra- and intermolecular amination of aromatic C–H bonds with aminium radicals generated from N-chloroamines under iron catalysis is reported. A range of substituted tetrahydroquinolines could be readily prepared, while extension to the synthesis of benzomorpholines was more limited in scope. A direct one-pot variant was developed, allowing direct formal oxidative N–H/C–H coupling.
Access to gem-Difluoro Olefins via C-H Functionalization and Dual Role of Anilines
Koenigs, Rene M.,Pei, Chao,Yang, Zhen
, p. 7234 - 7238 (2020)
In this Letter, we describe a simple, practical approach in which cheap CuI was used as a catalyst to introduce a gem-difluoro olefin onto simple electron-rich aniline derivatives in good yield via direct C-H functionalization and a subsequent HF elimination reaction. Detailed mechanistic studies point at a dual role of aniline derivatives in this reaction, which serve as a substrate and a basic promoter to trigger the HF elimination step.
Reductive: N -methylation of quinolines with paraformaldehyde and H2 for sustainable synthesis of N -methyl tetrahydroquinolines
Wang, Hongli,Huang, Yongji,Jiang, Qi,Dai, Xingchao,Shi, Feng
, p. 3915 - 3918 (2019)
A new and straightforward method was developed for the synthesis of N-methyl-1,2,3,4-tetrahydroquinolines by one-pot reductive N-methylation of quinolines with paraformaldehyde and H2 over Pd/C catalyst. A series of functional MTHQs, including (±)-galipinine and (±)-angustrureine were successfully synthesized in good to excellent yields by applying this simple catalyst system.
Novel borane reduction of ether-protected aromatic lactams
Hu, Wan-Ping,Tsai, Pei-Ching,Hsu, Ming-Kuan,Wang, Jeh-Jeng
, p. 3983 - 3985 (2004)
Borane reduction of ether-protected aromatic lactams produces 1-alkyl-1,2,3,4-tetrahydroquinolines (5 and 6) in excellent yields. This reaction provides a novel onepot tandem process for reduction of amide group and N-protected groups. Experimental results demonstrate that the reaction proceeds through two consecutive elimination and reductions via two C-O bond cleavages to form the foresaid products.
Investigation of excited state electron-transfer reactions. A search for other associative processes
De, R.,Bhattacharyya, S.,Ganguly, T.
, p. 325 - 336 (1994)
The present investigations were carried out to reveal the nature of the photoinduced electron-transfer (ET) process within the electron donors 1,2,3,4-tetrahydroquinoline (THQ) and 1-methyl-1,2,3,4-tetrahydroquinoline (THMe), and widely used acceptor tetracyanoquinodimethane (TCNQ) in the highly polar solvent acetonitrile (ACN) at 300 K.Observations of considerable overlapping between the emisson spectrum of the donor molecules studied in the present in the present investigation and the electronic absorption spectrum of the acceptor TCNQ, coupled to a high negative value of ΔG when one of the chromophores is excited, indicate the possibility of concurrent occurrence of the two processes, e.g. energy and electron transfer.Surprisingly even when the donor chromophore is photoexcited, no spectral manifestation of energy transfer was observed, though both steady state and time resolved (in the time domain of nanosecond order) spectroscopic measurements strongly suggest the occurrence of a highly exothermic ET reaction within the present donor-acceptor systems.Furthermore such ET reactions have been suggested to occur between donor and acceptor separated by a large distance (ca. 7 Angstroem), and quenching of fluorescence emission of donor molecules is caused primarily due to outer sphere ET reactions with the acceptor.Measured electron transfer rates (kET) were found to be of much lower value (ca. 107 s-1).It is demonstrated that loose structure of the transient geminate ion pair complex is formed due to the encounter between excited acceptor (or donor) and unexcited donor (or acceptor), and due to this structural property, a stable anionic species (TCNQ- ion) is produced due to the rapid dissociation (probably in the picosecond time domain) of this excited complex.It is hinted that synthesis of biochromophoric systems in which the present donor and acceptor chromophore would be linked by a polymethylene type (?-type) spacer might be useful in building good photoconducting materials.
Photobehavior of mixed π*/ππ* triplets: Simultaneous detection of the two transients, solvent-dependent hydrogen abstraction, and reequilibration upon protein binding
Jornet, Dolors,Tormos, Rosa,Miranda, Miguel A.
, p. 10768 - 10774 (2011)
In the present work, a systematic study on hydrogen abstraction by the excited triplet states of 4-methoxybenzophenone (1) and 4,4′- dimethoxybenzophenone (2) from 1,4-cyclohexadiene (3), 4-methylphenol (4), 1,2,3,4-tetrahydroquinoline (5), and 1-methyl-1,2,3,4-tetrahydroquinoline (6) in different media has been undertaken. Laser flash photolysis (LFP) revealed that in nonpolar solvents, 1 and 2 triplets have a π* configuration with the typical benzophenone-like T-T absorption spectrum (?max ca. 525 nm). Conversely, in aqueous solution, transient absorption spectra with maxima at 450 and 680 nm, attributed to the ππ* triplet, were obtained. Quenching of 1 or 2 triplet by 3 led to ketyl radical formation with rate constants in the range of 106-108 M-1 s -1, being one order of magnitude higher in acetonitrile than in aqueous media. The rate constants of quenching by 4 and 5 were similar in both polar and nonpolar solvents; the highest value was found for 6 in acetonitrile ((6.3 to 6.9) - 109 M-1 s-1). For mechanistic insight, LFP of 1 or 2 in the presence of dimethoxybenzene as electron donor was performed. The results showed that in this case, triplet quenching is favored in aqueous solution. In addition, 2 included in human serum albumin (HSA) was submitted to LFP. The decay kinetics, monitored at 430 nm, fitted well with three lifetimes of 0.45, 1.4, and 14.4 ?s assignable to 2 in bulk solution and in site II or in site I of HSA, respectively. This assignment was confirmed by using oleic acid and ibuprofen as selective displacement probes.
Metal-free reduction of unsaturated carbonyls, quinones, and pyridinium salts with tetrahydroxydiboron/water
Li, Tiejun,Peng, Henian,Tang, Wenjun,Tian, Duanshuai,Xu, Guangqing,Yang, He
, p. 4327 - 4337 (2021/05/31)
A series of unsaturated carbonyls, quinones, and pyridinium salts have been effectively reduced to the corresponding saturated carbonyls, dihydroxybenzenes, and hydropyridines in moderate to high yields with tetrahydroxydiboron/water as a mild, convenient, and metal-free reduction system. Deuterium-labeling experiments have revealed this protocol to be an exclusive transfer hydrogenation process from water. This journal is
Heterogeneous Hydrogenation of Quinoline Derivatives Effected by a Granular Cobalt Catalyst
Timelthaler, Daniel,Topf, Christoph
, (2021/11/22)
We communicate a convenient method for the pressure hydrogenation of quinolines in aqueous solution by using a particulate cobalt-based catalyst that is prepared in situ from simple Co(OAc)2 4H2O through reduction with abundant zinc powder. This catalytic protocol permits a brisk and atom-efficient access to a variety of 1,2,3,4-tetrahydroquinolines thereby relying solely on easy-to-handle reagents that are all readily obtained from commercial sources. Both the reaction setup assembly and the autoclave charging procedure are conducted on the bench outside an inert-gas-operated containment system, thus rendering the overall synthesis time-saving and operationally very simple.
Borane-Trimethylamine Complex as a Reducing Agent for Selective Methylation and Formylation of Amines with CO2
Zhang, Yanmeng,Zhang, He,Gao, Ke
supporting information, p. 8282 - 8286 (2021/10/25)
We report herein that a borane-trimethylamine complex worked as an efficient reducing agent for the selective methylation and formylation of amines with 1 atm CO2 under metal-free conditions. 6-Amino-2-picoline serves as a highly efficient catalyst for the methylation of various secondary amines, whereas in its absence, the formylation of primary and secondary amines was achieved in high yield with high chemoselectivity. Mechanistic studies suggest that the 6-amino-2-picoline-borane catalytic system operates like an intramolecular frustrated Lewis pair to activate CO2.
CO2-tuned highly selective reduction of formamides to the corresponding methylamines
Chao, Jianbin,Guo, Zhiqiang,Pang, Tengfei,Wei, Xuehong,Xi, Chanjuan,Yan, Leilei
supporting information, p. 7534 - 7538 (2021/10/12)
We herein describe an efficient, CO2-tuned and highly selective C-O bond cleavage of N-methylated formanilides. With easy-to-handle and commercially available NaBH4 as the reductant, a variety of formanilides could be turned into the desired tertiary amines in moderate to excellent yields. The role of CO2 has been investigated in detail, and the mechanism is proposed on the basis of experiments.
