1006-94-6Relevant articles and documents
A continuous protodecarboxylation of heteroaromatic carboxylic acids in sulfolane
Tilstam, Ulf
, p. 1449 - 1454 (2012)
A versatile, scalable method for the decarboxylation of indole-2-carboxylic acids has been found. With one equivalent of DBU in sulfolane, indole-2-carboxylic acid derivatives were cleanly decarboxylated in a 316 stainless steel tube reactor at 300 °C within 20 min. The corresponding indole derivatives were obtained in good yields. It was also found that indole-2-carboxylic acid (1) can be decarboxylated in either pure sulfolane or sulfolane with 3% water at 300 °C within 20 min. (1) The decarboxylation with one equivalent of DBU could successfully be transferred to benzo[b]thiophene-2-carboxylic acid derivatives if a prolonged reaction time was used. (2) Picolinic acid could also be decarboxylated in sulfolane with 3% water, and thiophene-2-carboxylic acid was smoothly decarboxylated with DABCO instead of DBU. (3) Benzoic acid derivatives were either inert or decomposed under the reaction conditions.
A highly active and recyclable catalyst for the synthesis of indole and phenyl ether
Qiao, Bo,Zhang, Le,Li, Rong
, p. 93463 - 93469 (2015)
A new simple catalytic system consisting of copper-aluminium and hydrotalcite (CuAl-HT) has been developed using a facile one-pot method without harm to the environment. The catalyst was characterized using TEM, XRD and XPS. It could be used as an efficient catalyst for the synthesis of both indole and phenyl ether. As expected, the catalyst afforded high catalytic activity for the selective synthesis of indole via intramolecular dehydrogenative N-heterocyclization of 2-(2-aminophenyl)ethanol. Meanwhile, it also exhibited superior catalytic properties for an Ullmann-type coupling reaction to synthesise phenyl ether from iodobenzene and phenol. The CuAl-HT catalyst showed higher activity than conventional catalysts based on copper and could be recycled several times with stable catalytic activity. This procedure has real economic advantages since no expensive materials were used.
Reevaluation of the 2-nitrobenzyl protecting group for nitrogen containing compounds: An application of flow photochemistry
Wendell, Chloe I.,Boyd, Michael J.
, p. 897 - 899 (2015)
Photochemistry under continuous flow conditions has many potential benefits for photochemical reactions that are problematic in batch. The 2-nitrobenzyl moiety is a photolabile protecting group for nitrogen. However, N-deprotection is generally impractical and, therefore, has not been extensively adopted. This Letter reports significant improvements in the N-deprotection of the 2-nitrobenzyl group through the application of continuous flow photolysis. This procedure was applied to a variety of substrates including indoles, indazoles, pyrazoles and secondary amines. Significant improvement in yield, reaction time and scalability was observed under continuous flow conditions.
Organo-Photoredox Catalyzed Oxidative Dehydrogenation of N-Heterocycles
Sahoo, Manoj K.,Jaiswal, Garima,Rana, Jagannath,Balaraman, Ekambaram
, p. 14167 - 14172 (2017)
We report here for the first time the catalytic oxidative dehydrogenation of N-heterocycles by a visible-light organo-photoredox catalyst with low catalyst loading (0.1–1 mol %). The reaction proceeds efficiently under base- and additive-free conditions with ambient air at room temperature. The utility of this benign approach is demonstrated by the synthesis of various pharmaceutically relevant N-heteroarenes such as quinoline, quinoxaline, quinazoline, acridine, and indole.
Ruthenium-catalysed synthesis of indoles from anilines and trialkanolamines in the presence of tin(II) chloride dihydrate
Cho, Chan Sik,Lim, Hyo Kyun,Shim, Sang Chul,Kim, Tae Jeong,Choi, Heung-Jin
, p. 995 - 996 (1998)
Anilines react with trialkanolamines in dioxane in the presence of a catalytic amount of a ruthenium catalyst together with tin(II) chloride dihydrate to give the corresponding indoles in moderate to good yields.
Acceptorless Dehydrogenation of N-Heterocycles by Merging Visible-Light Photoredox Catalysis and Cobalt Catalysis
He, Ke-Han,Tan, Fang-Fang,Zhou, Chao-Zheng,Zhou, Gui-Jiang,Yang, Xiao-Long,Li, Yang
, p. 3080 - 3084 (2017)
Herein, the first acceptorless dehydrogenation of tetrahydroquinolines (THQs), indolines, and other related N-heterocycles, by merging visible-light photoredox catalysis and cobalt catalysis at ambient temperature, is described. The potential applications to organic transformations and hydrogen-storage materials are demonstrated. Primary mechanistic investigations indicate that the catalytic cycle occurs predominantly by an oxidative quenching pathway.
Potassium tert-Butoxide-Promoted Acceptorless Dehydrogenation of N-Heterocycles
Liu, Tingting,Wu, Kaikai,Wang, Liandi,Yu, Zhengkun
, p. 3958 - 3964 (2019)
Potassium tert-butoxide-promoted acceptorless dehydrogenation of N-heterocycles was efficiently realized for the generation of N-heteroarenes and hydrogen gas under transition-metal-free conditions. In the presence of KOtBu base, a variety of six- and five-membered N-heterocyclic compounds efficiently underwent acceptorless dehydrogenation to afford the corresponding N-heteroarenes and H2 gas in o-xylene at 140 °C. The present protocol provides a convenient route to aromatic nitrogen-containing compounds and H2 gas. (Figure presented.).
Decarboxylation of indole-3-carboxylic acids under metal-free conditions
Chen, Xia,Zhou, Xiao-Yu
, p. 805 - 812 (2020)
Two reaction systems have been developed for the decarboxylation of indole-3-carboxylic acids. The decarboxylation can be achieved smoothly under K2CO3-catalyzed or acetonitrile-promoted basic conditions. It provided an efficient and simple method for the transformation of indole-3-carboxylic acids and the corresponding indoles were isolated with good to excellent yields. From the experimental facts, we put forward the possible reaction mechanism.
Superhydrophobic nickel/carbon core-shell nanocomposites for the hydrogen transfer reactions of nitrobenzene and N-heterocycles
Duan, Zhiying,Liu, Fangfang,Pang, Shaofeng,Su, Qiong,Wang, Yanbin,Xie, Xin,Zhang, Ping,Zhang, Yujing,Zhou, Feng
, p. 1996 - 2010 (2020)
In this work, catalytic hydrogen transfer as an effective, green, convenient and economical strategy is for the first time used to synthesize anilines and N-heterocyclic aromatic compounds from nitrobenzene and N-heterocycles in one step. Nevertheless, how to effectively reduce the possible effects of water on the catalyst by removal of the by-product water, and to further introduce water as the solvent based on green chemistry are still challenges. Since the structures and properties of carbon nanocomposites are easily modified by controllable construction, a one step pyrolysis process is used for controllable construction of micro/nano hierarchical carbon nanocomposites with core-shell structures and magnetic separation performance. Using various characterization methods and model reactions the relationship between the structure of Ni?NCFs (nickel-nitrogen-doped carbon frameworks) and catalytic performance was investigated, and the results show that there is a positive correlation between the catalytic performance and hydrophobicity of catalysts. Besides, the possible catalytically active sites, which are formed by the interaction of pyridinic N and graphitic N in the structure of nitrogen-doped graphene with the surfaces of Ni nanoparticles, should be pivotal to achieving the relatively high catalytic performance of materials. Due to its unique structure, the obtained Ni?NCF-700 catalyst with superhydrophobicity shows extraordinary performances toward the hydrogen transfer reaction of nitrobenzene and N-heterocycles in the aqueous state; meanwhile, it was also found that Ni?NCF-700 still retained its excellent catalytic activity and structural integrity after three cycles. Compared with traditional catalytic systems, our catalytic systems offer a highly effective, green and economical alternative for nitrobenzene and N-heterocycle transformation, and may open up a new avenue for simple construction of structure and activity defined carbon nanocomposite heterogeneous catalysts with superhydrophobicity.
High-Temperature Boc Deprotection in Flow and Its Application in Multistep Reaction Sequences
Bogdan, Andrew R.,Charaschanya, Manwika,Dombrowski, Amanda W.,Wang, Ying,Djuric, Stevan W.
, p. 1732 - 1735 (2016)
A simplified Boc deprotection using a high-temperature flow reactor is described. The system afforded the qualitative yield of a wide variety of deprotected substrates within minutes using acetonitrile as the solvent and without the use of acidic conditions or additional workups. Highly efficient, multistep reaction sequences in flow are also demonstrated wherein no extraction or isolation was required between steps.
Carbon-catalyzed Dehydrogenation of Indolines: Detection of Active Intermediate and Exploration of High-performance Catalyst
Morimoto, Naoki,Takeuchi, Yasuo,Nishina, Yuta
, p. 21 - 23 (2016)
Metal-free oxidation of indoline using molecular oxygen as an oxidant was investigated. Among various carbon-based catalysts, we found that reduced graphene oxide (rGO) was the most active. Superoxide radical was formed in the course of the reaction. Although graphene oxide (GO) did not function as a catalyst, rGO could be recycled at least 5 times without any structural change.
Deformylation of indole and azaindole-3-carboxaldehydes using anthranilamide and solid acid heterogeneous catalyst via quinazolinone intermediate
Yadav, Rammohan R.,Battini, Narsaiah,Mudududdla, Ramesh,Bharate, Jaideep B.,Muparappu, Nagaraju,Bharate, Sandip B.,Vishwakarma, Ram A.
, p. 2222 - 2225 (2012)
The deformylation of indole and azaindole-3-carboxaldehydes was achieved in the presence of anthranilamide and a solid acid heterogeneous catalyst under reflux conditions in 25-90% yield. The reaction proceeds via quinazolinone intermediate, which undergoes acid catalyzed cleavage to form deformylated product.
Room temperature catalytic dehydrogenation of cyclic amines with the liberation of H2 using water as a solvent
Sahoo, Manoj K.,Balaraman, Ekambaram
, p. 2119 - 2128 (2019)
Catalytic dehydrogenation of cyclic amines, in particular partially saturated N-heterocycles to N-heterocyclic arenes, with the removal of molecular hydrogen as the sole byproduct in water is reported. This dehydrogenation reaction proceeds smoothly under very mild and benign conditions and operates at room temperature. This distinctive reactivity has been achieved under dual catalytic conditions by merging the visible-light active [Ru(bpy)3]2+ as the photoredox catalyst and a newly synthesized cobalt complex as the proton-reduction catalyst. A detailed mechanistic study (control experiments, electrochemical studies, UV-visible experiments) is presented for the present dual catalysis.
Aerobic Dehydrogenation of N-Heterocycles with Grubbs Catalyst: Its Application to Assisted-Tandem Catalysis to Construct N-Containing Fused Heteroarenes
Kawauchi, Daichi,Noda, Kenta,Komatsu, Yoshiyuki,Yoshida, Kei,Ueda, Hirofumi,Tokuyama, Hidetoshi
, p. 15793 - 15798 (2020)
An aerobic dehydrogenation of nitrogen-containing heterocycles catalyzed by Grubbs catalyst is developed. The reaction is applicable to various nitrogen-containing heterocycles. The exceptionally high functional group compatibility of this method was confirmed by the oxidation of an unprotected dihydroindolactam V to indolactam V. Furthermore, by taking advantage of the oxygen-mediated structural change of the Grubbs catalyst, we integrated ring-closing metathesis and subsequent aerobic dehydrogenation to develop the novel assisted-tandem catalysis using molecular oxygen as a chemical trigger. The utility of the assisted-tandem catalysis was demonstrated by the concise synthesis of N-containing fused heteroarenes including a natural antibiotic, pyocyanine.
A mild and efficient dehydrogenation of indolines
Tilstam, Ulf,Harre, Michael,Heckrodt, Thilo,Weinmann, Hilmar
, p. 5385 - 5387 (2001)
A new mild and efficient dehydrogenation of indolines to indoles has been developed. For the dehydrogenation trichloroisocyanuric acid is used in combination with DBU. After work-up with sodium hydrogen sulfite it was possible to obtain indole in an almost quantitative yield. The new method is also suitable for indolines bearing electron withdrawing or electron donating groups. Under the reaction conditions no ring chlorination was observed.
Visible-Light-Promoted Efficient Aerobic Dehydrogenation of N-Heterocycles by a Tiny Organic Semiconductor Under Ambient Conditions
Su, Chenliang,Yu, Kunyi,Zhang, Hanjie,Zhu, Yongfa
, p. 1956 - 1960 (2020)
An efficient reusable catalytic system has been developed based on perylene diimide (PDI) organic semiconductor for the aerobic dehydrogenation of N-heterocycles with visible light. This practical catalytic system without any additives proceeds under ambient conditions. The minute aggregates of PDI molecules on the surface of SiO2 nanospheres form tiny organic semiconductors, resulting in high-efficiency photo-oxidative activity. Notably, the robustness of this method is demonstrated by the synthesis of a wide range of N-heteroarenes, gram-scale experiments as well as reusability tests.
Dehydrogenative N-heterocyclization of 2-(2-aminoaryl)ethyl alcohols to indole derivatives catalyzed by (μ-oxo)tetraruthenium cluster/1,2- bis(diphenylphosphino)benzene
Kondo, Teruyuki,Kanda, Takashi,Takagi, Daisuke,Wada, Kenji,Kimura,Toshimitsu, Akio
, p. 1015 - 1022 (2012)
A novel catalyst system of (μ-oxo)tetraruthenium cluster (2) combined with 1,2-bis(diphenylphosphino)benzene (dppbz) realized a simple, selective, and practical synthesis of indole and its derivatives from 2-(2-aminoaryl)ethyl alcohols via dehydrogenative N-heterocyclization reaction. Spontaneous formation of a stoichiometric amount of hydrogen (H2) was observed, and the present reaction proceeded smoothly under an argon atmosphere without oxidants and/or hydrogen acceptors.
Gold(III)-Catalyzed Decarboxylative C3-Benzylation of Indole-3-carboxylic Acids with Benzylic Alcohols in Water
Hikawa, Hidemasa,Kotaki, Fumiya,Kikkawa, Shoko,Azumaya, Isao
, p. 1972 - 1979 (2019)
A strategy for the gold(III)-catalyzed decarboxylative coupling reaction of indole-3-carboxylic acids with benzylic alcohols has been developed. This cascade reaction is devised as a straightforward and efficient synthetic route for 3-benzylindoles in moderate to excellent yields (50-93%). A Hammett study of the protodecarboxylation gives a negative ρ value, suggesting that there is a buildup of positive charge on the indole ring in the transition state. Furthermore, comparison of initial rates in H2O and in D2O reveals an observed kinetic solvent isotope effect (KSIE = 2.7). This simple protocol, which affords the desired products with CO2 and water as the coproducts, can be achieved under mild conditions without the need for base or other additives in water.
Tandem Wittig – Reductive annulation decarboxylation approach for the synthesis of indole and 2-substituted indoles
Volvoikar, Prajesh S.,Tilve
, p. 1851 - 1854 (2018)
A simple tandem Wittig reaction-reductive decarboxylation route is established for the synthesis of indoles from commercially available o-nitrobenzaldehydes and a stable phosphorane. The method allows access to indoles in a very fast manner without involving any metal or expensive reagents or inert atmosphere. Also 2-substituted indoles are obtained which forms an important core of many biological active compounds.
Metal–Organic Layers Hierarchically Integrate Three Synergistic Active Sites for Tandem Catalysis
Quan, Yangjian,Lan, Guangxu,Shi, Wenjie,Xu, Ziwan,Fan, Yingjie,You, Eric,Jiang, Xiaomin,Wang, Cheng,Lin, Wenbin
supporting information, p. 3115 - 3120 (2020/12/09)
We report the design of a bifunctional metal–organic layer (MOL), Hf12-Ru-Co, composed of [Ru(DBB)(bpy)2]2+ [DBB-Ru, DBB=4,4′-di(4-benzoato)-2,2′-bipyridine; bpy=2,2′-bipyridine] connecting ligand as a photosensitizer and Co(dmgH)2(PPA)Cl (PPA-Co, dmgH=dimethylglyoxime; PPA=4-pyridinepropionic acid) on the Hf12 secondary building unit (SBU) as a hydrogen-transfer catalyst. Hf12-Ru-Co efficiently catalyzed acceptorless dehydrogenation of indolines and tetrahydroquinolines to afford indoles and quinolones. We extended this strategy to prepare Hf12-Ru-Co-OTf MOL with a [Ru(DBB)(bpy)2]2+ photosensitizer and Hf12 SBU capped with triflate as strong Lewis acids and PPA-Co as a hydrogen transfer catalyst. With three synergistic active sites, Hf12-Ru-Co-OTf competently catalyzed dehydrogenative tandem transformations of indolines with alkenes or aldehydes to afford 3-alkylindoles and bisindolylmethanes with turnover numbers of up to 500 and 460, respectively, illustrating the potential use of MOLs in constructing novel multifunctional heterogeneous catalysts.
Iron-Catalyzed ?±,?-Dehydrogenation of Carbonyl Compounds
Zhang, Xiao-Wei,Jiang, Guo-Qing,Lei, Shu-Hui,Shan, Xiang-Huan,Qu, Jian-Ping,Kang, Yan-Biao
supporting information, p. 1611 - 1615 (2021/03/03)
An iron-catalyzed α,β-dehydrogenation of carbonyl compounds was developed. A broad spectrum of carbonyls or analogues, such as aldehyde, ketone, lactone, lactam, amine, and alcohol, could be converted to their α,β-unsaturated counterparts in a simple one-step reaction with high yields.
