55030-49-4Relevant academic research and scientific papers
Overcoming Electron-Withdrawing and Product-Inhibition Effects by Organocatalytic Aerobic Oxidation of Alkylpyridines and Related Alkylheteroarenes to Ketones
Wang, Hua,Liu, Jie,Qu, Jian-Ping,Kang, Yan-Biao
, p. 3942 - 3948 (2020/03/23)
An organocatalyzed aerobic benzylic C-H oxidation of alkyl and aryl heterocycles has been developed. This transition metal-free method is able to overcome the electron-withdrawing effect as well as product-inhibition effects in heterobenzylic radical oxidation. A variety of ketones bearing N-heterocyclic groups could be prepared under relatively mild conditions with moderate to high yields.
Selective Acylation of Aryl- A nd Heteroarylmagnesium Reagents with Esters in Continuous Flow
Heinz, Benjamin,Djukanovic, Dimitrije,Ganiek, Maximilian A.,Martin, Benjamin,Schenkel, Berthold,Knochel, Paul
supporting information, p. 493 - 496 (2020/01/31)
A selective acylation of readily accessible organomagnesium reagents with commercially available esters proceeds at convenient temperatures and short residence times in continuous flow. Flow conditions allow us to prevent premature collapse of the hemiacetal intermediates despite noncryogenic conditions, thus furnishing ketones in good yields. Throughout, the coordinating ability of the ester and/or Grignard was crucial for the reaction outcome. This was leveraged by the obtention of several bisaryl ketones using 2-hydroxy ester derivatives as substrates.
Metal-Free Halogen(I) Catalysts for the Oxidation of Aryl(heteroaryl)methanes to Ketones or Esters: Selectivity Control by Halogen Bonding
Guha, Somraj,Sekar, Govindasamy
supporting information, p. 14171 - 14182 (2018/09/10)
Metal-free halogen(I) catalysts were used for the selective oxidation of aryl(heteroaryl)methanes [C(sp3)?H] to ketones [C(sp2)=O] or esters [C(sp3)?O]. The synthesis of ketones was performed with a catalytic amount of NBS in DMSO solvent. Experimental studies and density functional theory (DFT) calculations supported the formation of halogen bonding (XB) between the heteroarene and N-bromosuccinimide, which enabled imine–enamine tautomerism of the substrates. No additional activator was required for this crucial step. Isotope-labeling and other supporting experiments suggested that a Kornblum-type oxidation with DMSO and aerobic oxygenation with molecular oxygen took place simultaneously. A background XB-assisted electron transfer between the heteroarenes and halogen(I) catalysts was responsible for the formation of heterobenzylic radicals and, thus, the aerobic oxygenation. For selective acyloxylation (ester formation), a catalytic amount of iodine was employed with tert-butyl hydroperoxide in aliphatic carboxylic acid solvent. Several control reactions, spectroscopic studies, and Time-Dependent Density Functional Theory (TD–DFT) calculations established the presence of acetyl hypoiodite as an active halogen(I) species in the acetoxylation process. With the help of a selectivity study, for the first time we report that the strength of the XB interaction and the frontier orbital mixing between the substrates and acyl hypoiodites determined the extent of the background electron-transfer process and, thus, the selectivity of the reaction.
Iridium-Catalyzed Highly Enantioselective Transfer Hydrogenation of Aryl N-Heteroaryl Ketones with N-Oxide as a Removable ortho-Substituent
Liu, Qixing,Wang, Chunqin,Zhou, Haifeng,Wang, Baigui,Lv, Jinliang,Cao, Lu,Fu, Yigang
supporting information, p. 971 - 974 (2018/02/23)
A highly enantioselective transfer hydrogenation of non-ortho-substituted aryl N-heteroaryl ketones, using readily available chiral diamine-derived iridium complex (S,S)-1f as a catalyst and sodium formate as a hydrogen source in a mixture of H2O/i-PrOH (v/v = 1:1) under ambient conditions, is described. The chiral aryl N-heteroaryl methanols were obtained with up to 98.2% ee by introducing an N-oxide as a removable ortho-substituent. In contrast, no more than 15.1% ee was observed in the absence of an N-oxide moiety. Furthermore, the practical utility of this protocol was also demonstrated by gram-scale asymmetric synthesis of bepotastine besilate in 51% total yield and 99.9% ee.
Direct oxidation of the Csp3–H bonds of N-heterocyclic compounds to give the corresponding ketones using a reusable heterogeneous MnOx-N@C catalyst
Ren, Lanhui,Wang, Lianyue,Lü, Ying,Li, Guosong,Gao, Shuang
, p. 1216 - 1221 (2016/09/07)
Novel reusable MnOx-N@C catalyst has been developed for the direct oxidation of N-heterocycles under solvent-free conditions using TBHP as benign oxidant to give the corresponding N-heterocyclic ketones. The catalytic system exhibited a broad substrate scope and excellent regioselectivity, as well as being amenable to gram-scale synthesis. This MnOx-N@C catalyst also showed good reusability and was successfully recycled six times without any significant loss of activity.
Synergistic H4NI-AcOH Catalyzed Oxidation of the Csp3-H Bonds of Benzylpyridines with Molecular Oxygen
Ren, Lanhui,Wang, Lianyue,Lv, Ying,Li, Guosong,Gao, Shuang
supporting information, p. 2078 - 2081 (2015/05/13)
The oxidation of benzylpyridines forming benzoylpyridines was achieved based on a synergistic H4NI-AcOH catalyst and molecular oxygen in high yield under solvent-free conditions. This is the first nonmetallic catalytic system for this oxidation transformation using molecular oxygen as the oxidant. The catalytic system has a wide scope of substrates and excellent chemoselectivity, and this procedure can also be scaled up. The study of a preliminary reaction mechanism demonstrated that the oxidation of the Csp3-H bonds of benzylpyridines was promoted by the pyridinium salts formed by AcOH and benzylpyridines. The synergistic effect of H4NI-AcOH was also demonstrated by control experiments. (Figure Presented).
Synthesis of aryl(di)azinyl ketones through copper- and iron-catalyzed oxidation of the methylene group of aryl(di)azinylmethanes
De Houwer, Johan,Abbaspour Tehrani, Kourosch,Maes, Bert U. W.
supporting information; experimental part, p. 2745 - 2748 (2012/04/10)
Sustainable Oxidations: An oxidation method to transform aryl(di)azinylmethanes into aryl(di)azinyl ketones is described. Base metals (copper and iron) as catalysts in combination with O2 as the oxidant are used, which makes this method sustainable. The utility of this method is illustrated by the synthesis of 6-(4-methylbenzoyl)pyridine-2-carbaldehyde, which is an intermediate in the preparation of the drug Acrivastine. Copyright
Slow-onset, long-duration, alkyl analogues of methylphenidate with enhanced selectivity for the dopamine transporter
Froimowitz, Mark,Gu, Yonghong,Dakin, Les A.,Nagafuji, Pamela M.,Kelley, Charles J.,Parrish, Damon,Deschamps, Jeffrey R.,Janowsky, Aaron
, p. 219 - 232 (2007/10/03)
Methylphenidate analogues, in which the carbomethoxy has been replaced by an alkyl group and with different phenyl substituents, have been synthesized and tested in monoamine transporter assays. As predicted from a pharmacophore model, most of the RR/SS diastereomers showed high potency as dopamine reuptake inhibitors. Analogues with a 4-chlorophenyl group and an unbranched initial alkyl atom had consistently enhanced selectivity for the dopamine transporter. The most potent compounds were those with a three- or four-carbon chain. The "inactive" RS/SR diastereomers showed substantial activity when the phenyl substituent was 3,4-dichloro. On a locomotor assay, one compound was found to have a slow onset and a long duration of action. The activity of these compounds provides additional evidence for a conformational/superposition model of methylphenidate with cocaine-like structures. A ketone analogue, obtained by hydrogenating a previously described vinylogous amide, had activity similar to that of methylphenidate.
Synthesis and pharmacology of potential cocaine antagonists. 2. Structure-activity relationship studies of aromatic ring-substituted methylphenidate analogs
Deutsch, Howard M.,Shi, Qing,Gruszecka-Kowalik, Ewa,Schwer, Margaret M.
, p. 1201 - 1209 (2007/10/03)
As part of a program, to develop medications which can block the binding of cocaine to the dopamine transporter, yet spare dopamine uptake, a series of aromatic ring-substituted methylphenidate derivatives was synthesized and tested for inhibitory potency in [3H]WIN 35,428 binding and [3H]dopamine uptake assays using rat striatal tissue. Synthesis was accomplished by alkylation of 2-bromopyridine with anions derived from various substituted phenylacetonitriles. In most cases, erythro compounds were markedly less potent than the corresponding (±)-threo-methylphenidate (TMP; Ritalin) derivatives. The ortho-substituted compounds were much less potent than the corresponding meta- and/or para-substituted derivatives. The most potent compound against [3H]WIN 35,428 binding, m-bromo-TMP, was 20-fold more potent than the parent compound, whereas the most potent compound against [3H]dopamine uptake, m,p-dichloro-TMP, was 32-fold more potent. Threo derivatives with m-or p-halo substituents were more potent than TMP, while electron-donating substituants caused little change or a small loss of potency. All of the derivatives had Hill coefficients approaching unity, except m,p-dichloro-TMP, which had an nH of 2.0. Although the potency of the (±)-methylphenidate derivatives in the two assays was highly correlated (R2 = 0.986), the compounds m-chloro-, m-methyl-, and p-iodo-TMP were 4-5-fold more potent at inhibiting [3H]-WIN 35,428 binding than [3H]dopamine uptake (cocaine has a ratio of 2.3). These and other compounds may be promising candidates for further testing as potential partial agonists or antagonists of cocaine.
