- One-pot tandem synthesis of 2,3-unsubstituted indoles, an improved Leimgruber-Batchoindole synthesis
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A concise, fast and efficient one-pot methodology has been developed for preparing 2,3-unsubstituted indoles from 2-nitrotoluenes and dimethylformamide dimethyl acetal. Compared with the classical Leimgruber-Batcho reaction, such a one-pot process simplified the operation procedures, generated less by-products and chemical residues, and resulted in higher overall yields in a shorter reaction time.
- Chen, Jinchun,Zhang, Zhikai,Liu, Sujing,Yang, Cuiyun,Xia, Chuanhai
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- A BN Aromatic Ring Strategy for Tunable Hydroxy Content in Polystyrene
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BN 2-vinylnaphthalene, a BN aromatic vinyl monomer, is copolymerized with styrene under free radical conditions. Oxidation yields styrene–vinyl alcohol (SVA) statistical copolymers with tunable hydroxy group content. Comprehensive spectroscopic investigation provides proof of structure. Physical properties that vary systematically with hydroxy content include solubility and glass transition temperature. BN aromatic polymers represent a platform for the preparation of diverse functional polymeric architectures via the remarkable reaction chemistry of C?B bonds.
- van de Wouw, Heidi L.,Lee, Jae Young,Awuyah, Elorm C.,Klausen, Rebekka S.
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- Properties of tryptophan indole-lyase from a piezophilic bacterium, Photobacterium profundum SS9
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Tryptophan indole-lyase (Trpase), PBPRA2532, from Photobacterium profundum SS9, a piezophilic marine bacterium, has been cloned, expressed in Escherichia coli, and purified. The P. profundum Trpase (PpTrpase) exhibits similar substrate specificity as the enzyme from E. coli (EcTrpase). PpTrpase has an optimum temperature for activity at about 30 °C, compared with 53 °C for EcTrpase, and loses activity rapidly (t1/2 ～ 30 min) when incubated at 50 °C, while EcTrpase is stable up to 65 °C. PpTrpase retains complete activity when incubated more than 3 h at 0 °C, while EcTrpase has only about 20% remaining activity. Under hydrostatic pressure, PpTrpase remains fully active up to 100 MPa (986 atm), while EcTrpase exhibits only about 10% activity at 100 MPa. PpTrpase forms external aldimine and quinonoid intermediates in stopped-flow experiments with l-Trp, S-Et-l-Cys, S-benzyl-l-Cys, oxindolyl-l-Ala, l-Ala and l-Met, similar to EcTrpase. However, with l-Trp a gem-diamine is observed that decays to a quinonoid complex. An aminoacrylate is observed with l-Trp in the presence of benzimidazole, as was seen previously with EcTrpase [28] but not with S-Et-l-Cys. The results show that PpTrpase is adapted for optimal activity in the low temperature, high pressure marine environment.
- Phillips, Robert S.,Ghaffari, Rashin,Dinh, Peter,Lima, Santiago,Bartlett, Douglas
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- Origin of Stability and Inhibition of Cooperative Alkyne Hydrofunctionalization Catalysts
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New entries to the [Ru(Cp/Cp*)(PR2NR′2)(MeCN)]PF6 catalyst family were synthesized, including a Cp complex (R = Cy; R′ = Ph) and two Cp* complexes (R = Cy, Ph; R′ = Ph). These and other derivatives were used for the intramolecular hydroamination of 2-ethynylaniline to elucidate trends in catalytic lifetime and rate. The readily accessible [Ru(Cp)(PCy2NPh2)(MeCN)]PF6 derivative showed comparable lifetime to [Ru(Cp)(Pt?Bu2NPh2)(MeCN)]PF6, the previous optimal catalyst. Donor-free ‘active’ catalysts, [Ru(Cp/Cp*)(PCy2NPh2)]PF6, were prepared and their thermal stability was assessed. The relatively high stability of the Cp derivative was explained by the capacity of the PCy2NPh2 ligand to coordinate in a κ3-(P,P,Ar) mode, which protects the low-coordinate species. This coordination mode is inaccessible with the Cp* derivative. Additionally, [Ru(Cp*)(PCy2NPh2)]PF6 readily activated the C?Cl bond of the solvent dichloromethane. Variable time normalization analysis (VTNA) revealed that the indole product inhibited the catalyst [Ru(Cp)(PCy2NPh2)(MeCN)]PF6, which slowed catalytic rates.
- Chapple, Devon E.,Boyle, Paul D.,Blacquiere, Johanna M.
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- back-to-Front Indole Synthesis Using Silver(I) Catalysis: Unexpected C-3 Pyrrole Activation Mode Supported by DFT
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An efficient silver(I)-catalyzed method is reported for the synthesis of substituted indoles, most notably 5-hydroxy-derivatives, via π-acidic alkyne activation. Most methods for the preparation of indoles involve annulation of a benzene precursor, but the method reported herein is unusual in that pyrrole precursors are used. Density Functional Theory (DFT) studies suggest that these reactions proceed via initial activation of the pyrrole C-3 position before undergoing subsequent rearrangement, contradicting the conventional wisdom that pyrroles are more nucleophilic through C-2.
- Clarke, Aimee K.,Lynam, Jason M.,Taylor, Richard J. K.,Unsworth, William P.
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- Group VI metal-promoted endo-azacyclizations via alkyne-derived metal vinylidene carbenes
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The molybdenum-promoted cycloisomerization of terminal alkynes tethered to nitrogen nucleophiles is described. Reaction of N-carbamoyl alkynylamines with (Et3N)Mo(CO)5 affords cyclic enecarbamates. Similarly, cyclization of 2-ethynylaniline gives the isomeric indole heterocycle, although N-3- butynylaniline affords the cyclic metal azacarbene product.
- McDonald, Frank E.,Chatterjee, Arnab K.
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- Ultrathin Amorphous/Crystalline Heterophase Rh and Rh Alloy Nanosheets as Tandem Catalysts for Direct Indole Synthesis
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Heterogeneous noble-metal-based catalysis plays an essential role in the production of fine chemicals. Rh-based catalysts are one of the most active candidates for indole synthesis. However, it is still highly desired to develop heterogeneous Rh-based catalysts with high activity and selectivity. In this work, a general, facile wet-chemical method is reported to synthesize ultrathin amorphous/crystalline heterophase Rh and Rh-based bimetallic alloy nanosheets (NSs), including RhCu, RhZn, and RhRu. Impressively, the amorphous/crystalline heterophase Rh NSs exhibit enhanced catalytic activity toward the direct synthesis of indole compared to the crystalline counterpart. Importantly, the obtained amorphous/crystalline heterophase RhCu alloy NSs can further enhance the selectivity to indole of >99.9% and the conversion is 100%. This work demonstrates the importance of phase engineering and metal alloying in the rational design and synthesis of tandem heterogeneous catalysts toward fine chemical synthesis.
- Ge, Jingjie,Yin, Peiqun,Chen, Ye,Cheng, Hongfei,Liu, Jiawei,Chen, Bo,Tan, Chaoliang,Yin, Peng-Fei,Zheng, Hong-Xing,Li, Qiang-Qiang,Chen, Shuangming,Xu, Wenjie,Wang, Xiaoqian,Wu, Geng,Sun, Rongbo,Shan, Xiang-Huan,Hong, Xun,Zhang, Hua
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- Ruthenium-catalyzed intramolecular hydroamination of aminoalkynes
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Low-valent ruthenium complexes with a π-acidic ligand, such as Ru(η6-cot)(dmfm)2 [cot=1,3,5-cyclooctatriene, dmfm=dimethyl fumarate] and Ru3(CO)12, showed high catalytic activity for the intramolecular hydroamination of aminoalkynes. The reaction is highly regioselective, in which a nitrogen atom is selectively attached to an internal carbon of alkynes to give five-, six-, and seven-membered nitrogen heterocycles as well as indoles in good to high yields.
- Kondo, Teruyuki,Okada, Takumi,Suzuki, Toshiaki,Mitsudo, Take-Aki
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- A Reusable MOF-Supported Single-Site Zinc(II) Catalyst for Efficient Intramolecular Hydroamination of o-Alkynylanilines
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The exploitation of new and active earth-abundant metal catalysts is critical for sustainable chemical production. Herein, we demonstrate the design of highly efficient, robust, and reusable ZnII-bipyridine-based metal–organic framework (MOF) catalysts for the intramolecular hydroamination of o-alkynylanilines to indoles. Under similar conditions homogeneous catalytic systems mainly provide hydrolysate. Our results prove that MOFs support unique internal environments that can affect the direction of chemical reactions. The ZnII-catalyzed hydroamination reaction can be conducted without additional ligands, base, or acid, and is thus a very clean reaction system with regard to its environmental impact.
- Li, Beibei,Ju, Zhanfeng,Zhou, Mi,Su, Kongzhao,Yuan, Daqiang
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- Protonated carbonic acid and reactive intermediates in the acidic decarboxylation of indolecarboxylic acids
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Elucidation of the mechanism for decarboxylation of indolecarboxylic acids over a wide range of solution acidity reveals the importance of protonated carbonic acid (PCA) as a reaction intermediate. In concentrated acid, the initial addition of water to the carboxyl group of the indolecarboxylic acid leads to a hydrated species that is capable of releasing PCA upon rate-determining carbon-carbon bond cleavage. The overall process is catalytic in water and acid, implicating PCA as a potential carboxylating reagent in the microscopic reverse reaction.
- Vandersteen, Adelle A.,Mundle, Scott O.C.,Kluger, Ronald
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- DDQ as an electrocatalyst for amine dehydrogenation, a model system for virtual hydrogen storage
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2,3-Dichloro-5,6-dicyanobenzoquinone (DDQ) is an electrochemical oxidation catalyst for a secondary amine, a model system for virtual hydrogen storage by removal of a hydrogen equivalent from an amine; a computational study provides mechanistic information. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011.
- Luca, Oana R.,Wang, Ting,Konezny, Steven J.,Batista, Victor S.,Crabtree, Robert H.
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- Conversion of Amines into Imines by Swern Oxidation
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Indoline (1) and 2-methylindoline (2) have been converted into indole (3) and 2-methylindole (4), and dibenzylamine (7) and phenylbenzylamine (8) have been converted into the Schiff bases (9) and (10), by Swern oxidation; the methylthiomethyl amines (5), (6), (11), and (12) were the only other products formed.
- Keirs, David,Overton, Karl
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- Thermodynamics and kinetics of indole oligomerization: Preliminary results in aqueous sulfuric acid
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Reaction rates and equilibrium constants of indole dimerization and trimerization in aqueous sulfuric acid at 298 K are reported. The equilibrium of oligomerization is attained in about 4-5 h, and formation of oligomers with more than three monomeric unit
- Quartarone,Ronchin,Tortato,Vavasori
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- From ascorbigens to indolocarbazoles
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New methods of L-ascorbic acid derivatization with the use of polyfunctional indole-3-cabinols are described. Reaction of β-hydroxy-N-methyltryptamine and L-ascorbic acid gave lactame derivatives; (indol-3-yl)gylcolic and L-ascorbic acids produced 2-hydroxy-4-hydroxymethyl-3-(indol-3-yl)-)-cylopen-2-enone. Similarly 4-hydroxy-3-methoxyphenylglycolic and L-ascorbic acids yielded 2-hydroxy-3-(4-hydroxy-3-methoxyphenyl)-4-hydroxymethyl-cyclopen-2-enone. Properties of N-methoxyascorbigen (neoascorbigen) were investigated. Alkylation of L-ascorbic acid with polysubstituted pyrrolecarbinols led to pyrrole analogues of ascorbigen. Acidic transformation of 3-formylindole and 1-methyl-3-formylindole led to indolocarbazoles and triindolylmethane derivatives.
- Preobrazhenskaya, Maria N.,Korolev, Alexander M.,Rozhkov, Ilya I.,Yudina, Larisa N.,Lazhko, Eduard I.,Aiello, Enrico,Almerico, Anna Maria,Mingoia, Francesco
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- Nucleophilic dimerization of indoline under oxidative conditions
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Oxidation of indoline with 30% hydrogen peroxide in methanol in the presence of sodium tungstate affords the dimeric 3-oxo-1'H,3H- 2,3'-biindole-1-oxide.
- Kovalev, Igor S.,Kopchuk, Dmitry S.,Zyryanov, Grigory V.,Rusinov, Vladimir L.,Chupakhin, Oleg N.
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- Simultaneous chemosensing of tryptophan and the bacterial signal molecule indole by boron doped diamond electrode
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A simple and robust chemosensing approach using a boron-doped diamond (BDD) electrode has been developed and applied to analyze tryptophan (TRP) and indole during the growth of Escherichia coli in a complex growth medium. The bacterial enzyme tryptophanase catalyzes TRP to indole, an emerging signaling molecule. The process can now be monitored using electrochemistry, in a method far beyond the traditional identification protocols. Electroanalysis in a non-aqueous medium comprising acetonitrile (ACN) and tetrabutylammonium hexafluorophosphate (TBAH) is capable of separating the oxidation peak of TRP from that of indole. Mechanisms are postulated for the electrochemical oxidation of indole and TRP in ACN chosen because of its wider potential range, proton acceptor property, and solubilization of analytes. The electrochemical oxidation of TRP involves the elimination of two electrons. With a detection limit of 0.5 μM for both indole and TRP, this chemosensing approach is sufficient to monitor the level of these two biomolecules during the bacterial growth period.
- Buzid, Alyah,Reen, F. Jerry,O'Gara, Fergal,McGlacken, Gerard P.,Glennon, Jeremy D.,Luong, John H.T.
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- CYCLIC ALLYLAMINE/ENAMINE SYSTEMS-6 SOME REACTIONS OF 4-(INDOL-2-YLCARBONYL)-, 4-(INDOL-3-YLCARBONYL)- AND 4-(INDOL-3-YLMETHYL)-1,2,5,6-TETRAHYDRO-1-METHYLPYRIDINES
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Indol-3-yl 1-methyl-1,2,5,6-tetrahydropyridin-4-yl ketone (1d) can be isomerised to indol-3-yl 1-methyl-1,2,3,4-tetrahydropyridin-4-yl- ketone but the protonated form of this enamine could not be cyclised to the indole α-position.Both indol-2-yl 1-methyl-1,2,5,6-tetrahydropyridin-4-yl ketone (1c) and its isomer (1d) were cyclised to 5-membered ketones by mineral acid catalysed Michael-type addition of indole β- and α-positions respectively onto the unsaturated ketone systems.Ketone (1d) was transformed to 1-acetylindol-3-yl 3-acetyl-1,4,5,6-tetrahydropyridin-4-yl ketone by hot acetic anhydride.Strong base treatment of indol-3-yl(1,2,5,6-tetrahydropyridin-4-yl) methane caused isomeration of the double bond into conjugation with the indole rather than into the endocyclic enamine position.
- Martinez, Silvio J.,Dalton, Lesley,Joule, John A.
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- Evolution of the indole alkaloid biosynthesis in the genus Hordeum: Distribution of gramine and DIBOA and isolation of the benzoxazinoid biosynthesis genes from Hordeum lechleri
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Two indole alkaloids with defense related functions are synthesized in the genus Hordeum of the Triticeae. Gramine (3(dimethyl-amino-methyl)-indole) is found in H. spontaneum and in some varieties of H. vulgare, the benzoxazinoid 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one (DIBOA) is detected in H. roshevitzii, H. brachyantherum, H. flexuosum, H. lechleri. Biosynthesis of DIBOA and of gramine was found to be mutually exclusive in wild Hordeum species, indicating that there was selection against simultaneous expression of both pathways during evolution. The full set of genes required for DIBOA biosynthesis in H.lechleri was isolated and the respective enzyme functions were analyzed by heterologous expression. The cytochrome P450 genes Bx2-Bx5 demonstrate a monophyletic origin for H. lechleri, Triticum aestivum and Zea mays. HlBx2-HlBx5 share highest homology to the orthologous genes of T. aestivum. In contrast, the branch point enzyme of the DIBOA pathway, the indole-3-glycerol phosphate lyase BX1, might have evolved independently in H. lechleri. In all Hordeum species that synthesize DIBOA, DNA sequences homologous to Bx genes are found. In contrast, these sequences are not detectable in the genomes of H. vulgare and H. spontaneum that do not synthesize benzoxazinoids.
- Gruen, Sebastian,Frey, Monika,Gierl, Alfons
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- Acceptorless dehydrogenation of N-heterocycles by supported Pt catalysts
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Pt metal nanoparticles loaded on various supports and carbon-supported various metal catalysts are tested for dehydrogenation of 6-methyl-1,2,3,4- tetrahydroquinoline to 6-methyl-quinoline under oxidant-free conditions. In the 20 types of the catalysts screened, carbon-supported Pt catalyst (Pt/C) shows the highest activity. Pt/C is reusable after the reaction and is effective for dehydrogenation of various N- heterocycles (tetrahydroquinolines and indoline). Pt/C is also effective for hydrogenation of quinoline under 3 bar H2. The results demonstrate that this catalytic method may be useful for an organic hidride–based hydrogen storage system.
- Moromi, Sondomoyee K.,Siddiki,Kon, Kenichi,Toyao, Takashi,Shimizu, Ken-ichi
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- Reaction pathway in the vapour-phase synthesis of indole and alkylindoles
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The vapour-phase synthesis of indole and its derivatives from aniline or alkylanilines and ethylene glycol or other diols was investigated with the use of a novel ZrO2/SiO2 (5:95 w/w) catalyst to check the applicability of this synthesis to a wide number of alkylindoles. During feeding with alkylaniline, the above catalyst showed catalytic results better than those reported in the literature, and a very good regenerability. In particular, with ethylene glycol, the best yields in the corresponding indoles were obtained when a C2-C3 alkyl chain was located in the ortho position to the amino group. The differences in reactivity between aniline and alkylaniline were significantly reduced when the length of the diol chain was increased and eliminated with 2,3-butanediol. On the basis of the above data and those collected sharing the synthesis in single steps, a possible overall reaction pathway was proposed to design a better tailor-made catalyst. It was also indicated that the formation of heavy compounds, which are able to deactivate the catalyst, were not derived from the reagents or the following reactions on the indole formed, but might be mainly attributed to the polycondensation of an aldehyde intermediate.
- Campanati,Franceschini,Piccolo,Vaccari
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- Electron Transfer From Indoles, Phenol, and Sulfite (SO32-) to Chlorine Dioxide (ClO2.)
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With the ClO2/ClO2- couple as reference the one-electron-reduction potentials have been determined for four methylated indolyl radical cations.Their Eo values are 1.23 V (N-Me), 1.10 V (2-Me), 1.07 V (3-Me), and 0.93 V (2,3-diMe).Eo values were also measured for the following: tryptophylH.+/trypH 1.24 V, SO3.-/SO32- 0.76 V, and phenoxy./phenolate 0.80 V.The redox potentials were obtained from purely kinetic data (for tryptophan and 2-, 3-, and N-methylindole) or from combined kinetic and thermodynamic measurements.
- Merenyi, Gabor,Lind, Johan,Shen, Xinhua
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- Radicals and radical ions derived from indole, indole-3-carbinol and diindolylmethane
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The primary products, i.e., the radical cations and radicals obtained on oxidation of the glucobrassicin metabolites (and dietary supplements), indole-3-carbinol (I3C) and diindolylmethane (DIM), and those from parent indole (I) are characterized in an ionic liquid and in Ar matrices. The radical cations of I and I3C are stable toward (photo)deprotonation under these conditions, but the resulting radicals can be generated by UV-photolysis of the neutral precursors. Two types of radicals, obtained by loss of hydrogen from N- and C-atoms, respectively, are found for I3C and DIM.
- Bloch-Mechkour, Anna,Bally, Thomas,Sikora, Adam,Michalski, Radoslaw,Marcinek, Andrzej,Gebicki, Jerzy
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- Transition metal-free regioselective C-3 amidation of indoles with N-fluorobenzenesulfonimide
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A direct transition metal-free regioselective C-3 amidation of indoles has been developed with the commercially available N-fluorobenzenesulfonimide (NFSI) as the amino source under external oxidant-free conditions. This amidation requires only a catalytic amount of base and exhibits excellent functional group tolerance and regioselectivity. The C-3 regioselectivity was proposed to realize by a free radical mechanism. Copyright
- Liu, Hai-Hong,Wang, Yi,Deng, Guojun,Yang, Luo
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- Striking effects of a titania support on the low-temperature activities of Ir catalysts for the dehydrogenative synthesis of benzimidazole and indole
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The crystalline structure of titania supports for iridium catalysts markedly affected their low-temperature activity for the dehydrogenative synthesis of N-containing heteroaromatics, namely benzimidazole and indole. While solid iridium catalysts supported on anatase showed moderate to poor activity for the synthesis of 2-phenylbenzimidazole (3) from o-phenylenediamine (1) and benzyl alcohol (2) at 100 °C, the reaction in the presence of rutile-supported catalysts proceeded smoothly to give 3 in high yields of up to 88%. Similar results were observed for the dehydrogenative conversion of 2-(2-aminophenyl)-ethanol (4) to indole (5). The reaction at 100 °C for 18 h in the presence of 1.0 mol% iridium on rutile gave 5 in a yield of 73%, while the use of anatase-supported catalysts resulted in significantly lower yields. TEM analysis showed the formation of small (ca. 2 nm in diameter), homogeneously-dispersed iridium nanoparticles on rutiles, while the inhomogeneous loading of iridium species was observed on anatase supports. CO pulse experiments revealed that there is a strong correlation between CO uptake by iridium nanoparticles and the activities at 100 °C. These results suggest that the predominant formation of small, well-reduced iridium nanoparticles is one major reason for the excellent activities of rutile-supported catalysts at low temperatures.
- Fukutake, Tatsuhiro,Wada, Kenji,Liu, Gang Chuan,Hosokawa, Saburo,Feng, Qi
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- The Catalytic Life of CdBr2-KBr and Its Affect on the Rate of Indole Formation from Aniline and Ethylene Glycol
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In the liquid-phase synthesis of indole from aniline and ethylene glycol (EG), a CdBr2-KBr catalyst gave a high yield of indole.In recycling experiments using the catalyst in an autoclave, the yield of indole remained stable and the inorganic comonents of the catalysts did not suffer degeneration.The time course of the reaction under pressure and high temperature was evaluated using a newly devised autoclave.The rate of formation of indole was determined to be proportional to the concentrations of both EG and the catalyst.Based on these findings for the reaction over CdBr2-3KBr, it is clear that this catalyst provides a simple and low-cost catalytic process for the formation of indole.
- Seto, Takatoshi,Kujira, Katsufumi,Iwane, Hiroshi,Imanari, Makoto
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- OXIDATIVE DECARBOXYLATION OF CYCLIC AMINO ACIDS AND DEHYDROGENATION OF CYCLIC SECONDARY AMINES WITH IODOSOBENZENE
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Cyclic amino acids L-proline, pipecolinic acid and L-2-pyrrolidinone-5-carboxylic acid undergo oxidative decarboxylation with iodosobenzene in various solvents (including water) to yield the lactam and imide in the latter case.The reaction proceeds via initial imine formation.
- Ochiai, Masahito,Inenaga, Minako,Nagao, Yoshimitsu,Moriarty, Robert M.,Vaid, Radhe K.,Duncan, Michael P.
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- 2,2,6,6-Tetramethylpiperidin-1-yloxycarbonyl: A Protecting Group for Primary, Secondary, and Heterocyclic Amines
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The 2,2,6,6-tetramethylpiperidin-1-yloxycarbonyl (Tempoc) protecting group is readily introduced by the reaction of amines with a new acyl transfer reagent, 4-nitrophenyl (2,2,6,6-tetramethylpiperidin-1-yl) carbonate (NPTC). Tempoc has a reactivity profile that complements the commonly used t-butyloxycarbonyl (Boc) and benzyloxycarbonyl (Cbz) protecting groups. Deprotection can be achieved under mild reductive conditions with in situ generated Cu(I) species or by thermolytic cleavage at 135 °C. Mechanistic studies on the deprotection of Tempoc-indole suggest a combination of ionic and radical fragmentation pathways under thermal conditions.
- Lizza, Joseph R.,Bremerich, Maximilian,McCabe, Stephanie R.,Wipf, Peter
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- SUBSTITUTION NUCLEOPHILE RADICALAIRE (SRN1) INDUITE PAR VOIE ELECTROCHIMIQUE
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The electrochemical method is used for initiate a radical nucleophilic substitution leading to the synthesis of indoles.
- Boujlel, K.,Simonet, J.,Roussi, G.,Beugelmans, R.
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- NH4Cl-promoted synthesis of symmetrical and unsymmetrical triindolylmethanes under solvent-free conditions
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The synthesis of various triindolylmethanes from indole-3-carboxaldehyde, using indole derivatives as reactants and NH4Cl as catalyst under solvent-free conditions, is described. This methodology provides access to both symmetrical and unsymmetrical triindolylmethanes in excellent yields. With N-methylindole particularly, indole-3-carboxaldehyde appears to act as a formyl donor, leading to the exclusive formation of a symmetrically trisubstituted product. The novelty of the methodology lies in its operational simplicity, environment friendly reaction conditions, and inexpensive and easy availability of the catalyst. A plausible mechanism of formation of the products is suggested.
- Naskar, Subhendu,Hazra, Abhijit,Priyankar Paira,Sahu, Rishnendu B.,Banerjee, Sukdeb,Mondal, Nirup B.
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- Pyrylenes: A New Class of Tunable, Redox-Switchable, Photoexcitable Pyrylium-Carbene Hybrids with Three Stable Redox-States
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A new synthetic and modular access to a large family of redox-switchable molecules based upon the combination of pyrylium salts and carbenes is presented. The redox-properties of this new molecule class correlate very well with the π-accepting properties of the corresponding carbenes. While the pyrylium moiety acts as a chromophore, the carbene moiety can tune the redox-properties and stabilize the corresponding radicals. This leads to the isolation of the first monomeric pyranyl-radical in the solid-state. The three stable oxidation states could be cleanly accessed by chemical oxidation, characterized by NMR, EPR, UV-vis, and X-ray diffraction and supported by (TD)-DFT-calculations. The new hybrid class can be utilized as an electrochemically triggered switch and as a powerful photoexcited reductant. Importantly, the pyrylenes can be used as novel photocatalysts for the reductive activation of aryl halides and sulfonamides by consecutive visible light induced electron transfer processes.
- Antoni, Patrick W.,Hansmann, Max M.
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- Proton transfer and carbon-carbon bond cleavage in the elimination of indole catalyzed by Escherichia coli tryptophan indole-lyase
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Tryptophan indole-lyase from Escherichia coli catalyzes the reversible cleavage of L-tryptophan to indole and ammonium pyruvate. This reaction is mechanistically interesting since it involves the elimination of an aromatic carbon leaving group. We have been studying the mechanism of tryptophan indole-lyase using rapid-scanning stopped-flow spectrophotometry. Recently, we demonstrated that the rate constant for α-aminoacrylate intermediate formation from α-2H-L-tryptophan exhibits an isotope effect of 3.0 (Sloan, M. J.; Phillips, R. S. Biochemistry 1996, 35, 16165-16173). We have confirmed this previous result (Dk = 2.99 ± 0.30) and we have now found that β,β-di-2H-L-tryptophan also exhibits a secondary isotope effect (Dk = 1.17 ± 0.03) on the elimination reaction. Furthermore, α,β,β-tri-2H-L-tryptophan exhibits a multiple isotope effect (Dk = 4.42 ± 0.67) on the elimination of indole. In addition, there is a significant solvent isotope effect (Dk = 1.79 ± 0.11) on indole elimination in D2O. This solvent isotope effect combines with the effect of α-deuterium, since elimination of α-2H-L-tryptophan in D2O exhibits Dk = 4.30 ± 0.16. In addition, the rate constant for indole elimination shows a linear Eyring plot between 5 and 35 °C. In the direction of tryptophan synthesis, the reaction of the α-aminoacrylate intermediate with indole to form a quinonoid intermediate also exhibits a kinetic isotope effect for 3-2H-indole, with Dk = 1.88 ± 0.19. In contrast to our expectations, the results suggest that the proton transfer and carbon-carbon bond cleavage in the elimination reaction are very nearly simultaneous and that the indolenine structure is a transient intermediate which occupies a very shallow well on the reaction coordinate, or a transition state, in the reaction of Trpase.
- Phillips, Robert S.,Sundararaju, Bakthavatsalam,Faleev, Nicolai G.
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- A NEW DEHYDROGENATION REACTION OF INDOLINES TO INDOLES VIA AZASULFONIUM SALTS
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Indolines (1) have been converted to the corresponding azasulfonium salts (2) and the subsequent intramolecular base catalyzed abstraction of the hydrogen at C-2 gave indoles (4) in good yields.
- Kikugawa, Yasuo,Kawase, Masami
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- Indole synthesis by palladium-catalyzed tandem allylic isomerization-furan Diels-Alder reaction
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A Pd(0)-catalyzed elimination of an allylic acetate generates a π-allyl complex that is postulated to initiate a novel intramolecular Diels-Alder cycloaddition to a tethered furan (IMDAF). Under the reaction conditions, this convergent, microwave-accelerated cascade process provides substituted indoles in moderate to good yields after Pd-hydride elimination, aromatization by dehydration, and in situ N-Boc cleavage.
- Xu, Jie,Wipf, Peter
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- Kinetics and mechanism of the basic hydrolysis of indomethacin and related compounds: A reevaluation
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The kinetics of the hydrolysis of indomethacin and related compounds were studied in an alkaline medium at 25°. The pseudo-first-order rate constants were evaluated from log absorbance versus time plots in the ultraviolet. These compounds showed a second-order rate constant at low concentrations of hydroxide ion and a first-order rate constant at higher concentrations of hydroxide ion.
- Cipiciani,Ebert,Linda,Rubessa,Savelli
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- Improved indole syntheses from anilines and vicinal diols by cooperative catalysis of ruthenium complex and acid
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By developing a new and efficient dinuclear catalyst [Ru(CO) 2(Xantphos)]2 [Xantphos = 4,5-bis(diphenylphosphino)-9,9- dimethyl-9H-xanthene], an improved synthesis of indole from vicinal diols and anilines by cooperative catalysis of ruthenium complex and p-TSA (para-toluenesufonic acid) has been demonstrated. The presented synthetic protocol allows assembling a wide range of products in an efficient manner. Comparing to the existed protocols, our indole syntheses can be achieved at lower reaction temperature, in shorter reaction time, and with improved substrate tolerance.
- Zhang, Min,Xie, Feng,Wang, Xiaoting,Yan, Fengxia,Wang, Ting,Chen, Mengmeng,Ding, Yuqiang
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- Effect of commitments to catalysis on the degree of curvature in proton inventories of the kinetic parameters for enzyme-catalyzed reactions: Application to tryptophan indole-lyase
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A relatively simple method for obtaining Dk, the intrinsic solvent deuterium isotope effect for an enzyme-catalyzed reaction, is presented and discussed. Steady-state and pre-steady-state determinations of the solvent deuterium and substrate deuterium isotope effects, the later obtained in both H2O and D2O, enable the development of a catalytic mechanism. The interrelatedness of the isotope effect equations for the enzyme system allows calculation of Dk. As a result, the variation of l/Dka, the reciprocal of the partial intrinsic solvent deuterium isotope effect, with n(D2O), the atom fraction of deuterium in mixed isotopic waters, has been determined for the tryptophan indole-lyase enzyme-catalyzed reaction, and is compared to the variation of (V/K)n/(V/K)0 with n(D2O). Comparison of the proton inventories indicates that without knowledge of the commitments to catalysis underestimates of the number of protons calculated from a fit of the kinetic parameter data to the Gross-Butler equation can occur. A series of curves is presented which demonstrate that the degree of curvature in a bowl-shaped proton inventory decreases as the commitment to catalysis increases, and that ultimately, as the relative size of the commitment continues to increase, a dome-shaped proton inventory will result.
- Kiick, Dennis M.
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- Efficient nickel-mediated intramolecular amination of aryl chlorides
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(Matrix presented) The use of an in situ generated Ni(0) catalyst associated with 2,2′-bipyridine or N,N′ -bis(2,6-diisopropylphenyl)dihydroimidazol-2-ylidene (SIPr) as a ligand and NaO-t-Bu as the base for the intramolecular coupling of aryl chlorides with amines is described. The procedure has been applied to the formation of five-, six-, and seven-membered rings.
- Omar-Amrani, Rafik,Thomas, Antoine,Brenner, Eric,Schneider, Raphael,Fort, Yves
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- Visible light-mediated decarboxylative amination of indoline-2-carboxylic acids catalyzed by Rose Bengal
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A visible light-induced decarboxylative amination of indoline-2-carboxylic acids and azodicarboxylate esters has been developed, in which the oxidation of α-amino acids provides a versatile CO2-extrusion platform to generate α-aminoalkyl radicals. The corresponding products were obtained with yields of up to 72% catalyzed by a metal-free photocatalyst under mild conditions.
- Zhang, Meng-Jie,Schroeder, Griffin M.,He, Yan-Hong,Guan, Zhi
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- A preparative synthesis of indole by dehydrogenation of 4,5,6,7-tetrahydroindole over catalysts with a low palladium content
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Catalysts containing 0.15 - 0.5 percent of Pd are highly active and selective in the dehydrogenation of 4,5,6,7-tetrahydroindole to indole when γ-Al2O3 or Sibunite are used as supports. - Keywords: Pd-containing catalysts, tetrahydroindole, indole, dehydrogenation.
- Ryashentseva, M. A.
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- Turning tryptophanase into odor-generating biosensors
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An odor-based sensor system that exploits the metabolic enzyme tryptophanase (TPase) as the key component is reported. This enzyme is able to convert an odorless substrate like S-methyl-L-cysteine or L-tryptophan into the odorous products methyl mercaptan or indole. To make a biosensor, TPase was biotinylated so that it could be coupled with a molecular recognition element, such as an antibody, to develop an ELISA-like assay. This method was used for the detection of an antibody present in nM concentrations by the human nose. TPase can also be combined with the enzyme pyridoxal kinase (PKase) for use in a coupled assay to detect adenosine 5-triphosphate (ATP). When ATP is present in the low μM concentration range, the coupled enzymatic system generates an odor that is easily detectable by the human nose. Biotinylated TPase can be combined with various biotin-labeled molecular recognition elements, thereby enabling a broad range of applications for this odor-based reporting system. The nose knows: Tryptophanase (TPase), which converts S-methyl-L-cysteine into methyl mercaptan (smelly), was coupled to a molecular recognition element (such as an antibody) to create an odor-based biosensor. Biotinylated TPase could be combined with various biotin-labeled molecular recognition elements, thereby enabling a broad range of applications for this odor-based reporting system.
- Xu, Yaqin,Zhang, Zhuyuan,Ali, M. Monsur,Sauder, Joanna,Deng, Xudong,Giang, Karen,Aguirre, Sergio D.,Pelton, Robert,Li, Yingfu,Filipe, Carlos D. M.
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- Ordered Porous Nitrogen-Doped Carbon Matrix with Atomically Dispersed Cobalt Sites as an Efficient Catalyst for Dehydrogenation and Transfer Hydrogenation of N-Heterocycles
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Single-atom catalysts (SACs) have been explored widely as potential substitutes for homogeneous catalysts. Isolated cobalt single-atom sites were stabilized on an ordered porous nitrogen-doped carbon matrix (ISAS-Co/OPNC). ISAS-Co/OPNC is a highly efficient catalyst for acceptorless dehydrogenation of N-heterocycles to release H2. ISAS-Co/OPNC also exhibits excellent catalytic activity for the reverse transfer hydrogenation (or hydrogenation) of N-heterocycles to store H2, using formic acid or external hydrogen as a hydrogen source. The catalytic performance of ISAS-Co/OPNC in both reactions surpasses previously reported homogeneous and heterogeneous precious-metal catalysts. The reaction mechanisms are systematically investigated using first-principles calculations and it is suggested that the Eley–Rideal mechanism is dominant.
- Han, Yunhu,Wang, Ziyun,Xu, Ruirui,Zhang, Wei,Chen, Wenxing,Zheng, Lirong,Zhang, Jian,Luo, Jun,Wu, Konglin,Zhu, Youqi,Chen, Chen,Peng, Qing,Liu, Qiang,Hu,Wang, Dingsheng,Li, Yadong
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- An Equilibrium and Calorimetric Investigation of the Hydrolysis of L-Tryptophan to (Indole + Pyruvate + Ammonia)
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Apparent equilibrium constants and calorimetric enthalpies of reaction have been measured for the reaction L-tryptophan(aq) + H2O(l) = indole(aq) + pyruvate(aq) + ammonia(aq) which is cataluzed by L-tryptophanase.High-pressure liquid-chromatography and microcalorimetery were used to perform these measurements.The equilibrium measurements were performed as a function of pH, temperature, and ionic strength.The results have been interpreted with a chemical equilibrium model to obtain thermodynamic quantities for the reference reaction: L-tryptophan(aq) + H2O(l)= indole(aq) + pyruvate-(aq) + NH4+(aq).At T=25 deg C and Im=0 the results for this reaction are: K0=(1.05+/-0.13)x10E-4, ΔrG0=(22.71+/-0.33) kJ-mol-1, ΔrH0=(62.0+/-2.3) kJ-mol-1, and ΔrS0=(132+/-8) J-K-1-mol-1.These results have been used together with thermodynamic results from the literature to calculate standard Gibbs energies of formation, standard enthalpies of formation, standard molar entropies, standard molar heat capacities, and standard transformed formation properties for the substances participating in this reaction.
- Tewari, Yadu B.,Goldberg, Robert N.
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- A biomass-derived N-doped porous carbon catalyst for the aerobic dehydrogenation of nitrogen heterocycles
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N-doped porous carbon (NC) was synthesized from sugar cane bagasse, which is a sustainable and widely available biomass waste. The preferred NC sample had a well-developed porous structure, a graphene-like surface morphology and different N species. More
- Cui, Fu-Jun,Guo, Fu-Hu,Liu, Jing-Jiang,Liu, Xiao-Yu,Quan, Zheng-Jun,Ullah, Arif,Wang, Xi-Cun,Zhu, Ji-Hua
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supporting information
p. 1791 - 1799
(2022/01/31)
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- Nickel-Catalyzed Addition of C–C Bonds of Amides to Strained Alkenes: The 1,2-Carboaminocarbonylation Reaction
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C(aryl)–C(═O) bonds of aryl amides can be activated and added across alkenes with the aid of a nickel catalyst. This 1,2-carboaminocarbonylation reaction enables the dicarbofunctionalization of alkenes with an atom economy of 100%.
- Ito, Yuri,Kodama, Takuya,Nakatani, Syun,Shiraki, Ryota,Tobisu, Mamoru
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supporting information
p. 662 - 666
(2022/02/05)
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- Chemoselective hydrosilylation of carboxylic acids using a phosphine-free ruthenium complex and phenylsilane
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A highly chemoselective hydrosilylation of carboxylic acids was achieved using a bench-stable, phosphine-free Ru-complex tethered with hemi-labile thiophene ligands as the catalyst, employing phenylsilane as the reducing agent. The methodology was further elaborated towards the one-pot synthesis of indole and benzoxazine via tandem reduction/cyclization of acid and nitro group.
- Abhilash, Vishwanathan,Gadakh, Amol V.,Ganesh, Sambasivam,Hegde, Shivaprasad N.,Jacob, Anand,Karthik, C. S.,Lamees, Thundianandi,Mathivanan, Namachivayam,Sathiyanarayanan, Arumugam Murugan
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supporting information
(2022/03/01)
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- Electrochemical Dearomative Dicarboxylation of Heterocycles with Highly Negative Reduction Potentials
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The dearomative dicarboxylation of stable heteroaromatics using CO2is highly challenging but represents a very powerful method for producing synthetically useful dicarboxylic acids, which can potentially be employed as intermediates of biologically active molecules such as natural products and drug leads. However, these types of transformations are still underdeveloped, and concise methodologies with high efficiency (e.g., high yield and high selectivity for dicarboxylations) have not been reported. We herein describe a new electrochemical protocol using the CO2radical anion (E1/2of CO2= -2.2 V in DMF and -2.3 V in CH3CN vs SCE) that produces unprecedented trans-oriented 2,3-dicarboxylic acids from N-Ac-, Boc-, and Ph-protected indoles that exhibit highly negative reduction potentials (-2.50 to -2.94 V). On the basis of the calculated reduction potentials, N-protected indoles with reduction potentials up to -3 V smoothly undergo the desired dicarboxylation. Other heteroaromatics, including benzofuran, benzothiophene, electron-deficient furans, thiophenes, 1,3-diphenylisobenzofuran, and N-Boc-pyrazole, also exhibit reduction potentials more positive than -3 V and served as effective substrates for such dicarboxylations. The dicarboxylated products thus obtained can be derivatized into useful synthetic intermediates for biologically active compounds in few steps. We also show how the dearomative monocarboxylation can be achieved selectively by choice of the electrolyte, solvent, and protic additive; this strategy was then applied to the synthesis of an octahydroindole-2-carboxylic acid (Oic) derivative, which is a useful proline analogue.
- Hayashi, Hiroki,Kanna, Wataru,Maeda, Satoshi,Mita, Tsuyoshi,Takano, Hideaki,You, Yong
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supporting information
p. 3685 - 3695
(2022/03/08)
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- Synthesis of Non-Terminal Alkenyl Ethers, Alkenyl Sulfides, and N-Vinylazoles from Arylaldehydes or Diarylketones, DMSO and O, S, N-Nucleophiles
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A transition-metal-free protocol for the synthesis of non-terminal alkenyl ethers, alkenyl sulfides, and N-vinylazoles from arylaldehydes or diarylketones, DMSO and O, S, N-nucleophiles has been reported. In this protocol, 24 examples of non-terminal alkenyl ethers and 28 examples of non-terminal alkenyl sulfides in 72–95% yields have been synthesized within 5 min. Moreover, 27 examples of non-terminal N-vinylazoles with 57–88% yields have also been synthesized within 2 hours. The preliminary mechanism investigations revealed that arylaldehydes or diarylketones offered a carbon atom, DMSO provided a methine and O, S, N-nucleophiles contributed one X atom for constructing C=C?X structure. (Figure presented.).
- Nie, Zhiwen,Lv, Huifang,Yang, Tonglin,Su, Miaodong,Luo, Weiping,Liu, Qiang,Guo, Cancheng
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supporting information
p. 1473 - 1480
(2022/04/03)
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- Metal–Organic Layers Hierarchically Integrate Three Synergistic Active Sites for Tandem Catalysis
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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.
- Quan, Yangjian,Lan, Guangxu,Shi, Wenjie,Xu, Ziwan,Fan, Yingjie,You, Eric,Jiang, Xiaomin,Wang, Cheng,Lin, Wenbin
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supporting information
p. 3115 - 3120
(2020/12/09)
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- Highly Ordered Mesoporous Cobalt Oxide as Heterogeneous Catalyst for Aerobic Oxidative Aromatization of N-Heterocycles
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N-heterocycles are key structures for many pharmaceutical intermediates. The synthesis of such units normally is conducted under homogeneous catalytic conditions. Among all methods, aerobic oxidative aromatization is one of the most effective. However, in homogeneous conditions, catalysts are difficult to be recycled. Herein, we report a heterogeneous catalytic strategy with a mesoporous cobalt oxide as catalyst. The developed protocol shows a broad applicability for the synthesis of N-heterocycles (32 examples, up to 99 % yield), and the catalyst presents high turnover numbers (7.41) in the absence of any additives. Such a heterogenous approach can be easily scaled up. Furthermore, the catalyst can be recycled by simply filtration and be reused for at least six times without obvious deactivation. Comparative studies reveal that the high surface area of mesoporous cobalt oxide plays an important role on the catalytic reactivity. The outstanding recycling capacity makes the catalyst industrially practical and sustainable for the synthesis of diverse N-heterocycles.
- Cao, Yue,Wu, Yong,Zhang, Yuanteng,Zhou, Jing,Xiao, Wei,Gu, Dong
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p. 3679 - 3686
(2021/06/18)
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- Luminescent Platinum(II) Complexes with Bidentate Diacetylide Ligands: Structures, Photophysical Properties and Application Studies
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A series of platinum(II) complexes supported by terphenyl diacetylide as well as diimine or bis-N-heterocyclic carbene (NHC) ligands have been prepared. The diacetylide ligands adopt a cis coordination mode featuring non-planar terphenyl moieties as revealed by X-ray crystallographic analyses. The electrochemical, photophysical and photochemical properties of these platinum(II) complexes have been investigated. These platinum(II) diimine complexes show broad emission with peak maxima from 566 nm to 706 nm, with two of them having emission quantum yields >60% and lifetimes 2 μs in solutions at room temperature, whereas the platinum(II) diacetylide complexes having bis-N-heterocyclic carbene instead of diimine ligand display photoluminescence with quantum yields of up to 28% in solutions and excited state lifetimes of up to 62 μs at room temperature. Application studies revealed that one of the complexes can catalyze photoinduced aerobic dehydrogenation of alcohols and alkenes, and a relatively non-toxic water-soluble Pt(II) complex displays anti-angiogenic activity.
- Luo, Zaoli,Liu, Yungen,Tong, Ka-Chung,Chang, Xiao-Yong,To, Wai-Pong,Che, Chi-Ming
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supporting information
p. 2978 - 2992
(2021/08/30)
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- Visible light mediated selective oxidation of alcohols and oxidative dehydrogenation of N-heterocycles using scalable and reusable La-doped NiWO4nanoparticles
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Visible light-mediated selective and efficient oxidation of various primary/secondary benzyl alcohols to aldehydes/ketones and oxidative dehydrogenation (ODH) of partially saturated heterocycles using a scalable and reusable heterogeneous photoredox catalyst in aqueous medium are described. A systematic study led to a selective synthesis of aldehydes under an argon atmosphere while the ODH of partially saturated heterocycles under an oxygen atmosphere resulted in very good to excellent yields. The methodology is atom economical and exhibits excellent tolerance towards various functional groups, and broad substrate scope. Furthermore, a one-pot procedure was developed for the sequential oxidation of benzyl alcohols and heteroaryl carbinols followed by the Pictet-Spengler cyclization and then aromatization to obtain the β-carbolines in high isolated yields. This methodology was found to be suitable for scale up and reusability. To the best of our knowledge, this is the first report on the oxidation of structurally diverse aryl carbinols and ODH of partially saturated N-heterocycles using a recyclable and heterogeneous photoredox catalyst under environmentally friendly conditions.
- Abinaya, R.,Balasubramaniam, K. K.,Baskar, B.,Divya, P.,Mani Rahulan, K.,Rahman, Abdul,Sridhar, R.,Srinath, S.
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p. 5990 - 6007
(2021/08/24)
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- Zwitterion-induced organic-metal hybrid catalysis in aerobic oxidation
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In many metal catalyses, the traditional strategy of removing chloride ions is to add silver salts via anion exchange to obtain highly active catalysts. Herein, we reported an alternative strategy of removing chloride anions from ruthenium trichloride using an organic [P+-N-] zwitterionic compound via multiple hydrogen bond interactions. The resultant organic-metal hybrid catalytic system has successfully been applied to the aerobic oxidation of alcohols, tetrahydroquinolines, and indolines under mild conditions. The performance of zwitterion is far superior to that of many other common Lewis bases or Br?nsted bases. Mechanistic studies revealed that the zwitterion triggers the dissociation of chloride from ruthenium trichloride via nonclassical hydrogen bond interaction. Preliminary studies show that the zwitterion is applicable to catalytic transfer semi-hydrogenation.
- Hu, Rong-Bin,Lam, Ying-Pong,Ng, Wing-Hin,Wong, Chun-Yuen,Yeung, Ying-Yeung
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p. 3498 - 3506
(2021/04/07)
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- Iron(II)-Catalyzed Aerobic Biomimetic Oxidation of N-Heterocycles
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Herein, an iron(II)-catalyzed biomimetic oxidation of N-heterocycles under aerobic conditions is described. The dehydrogenation process, involving several electron-transfer steps, is inspired by oxidations occurring in the respiratory chain. An environmentally friendly and inexpensive iron catalyst together with a hydroquinone/cobalt Schiff base hybrid catalyst as electron-transfer mediator were used for the substrate-selective dehydrogenation reaction of various N-heterocycles. The method shows a broad substrate scope and delivers important heterocycles in good-to-excellent yields.
- Manna, Srimanta,Kong, Wei-Jun,B?ckvall, Jan-E.
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supporting information
p. 13725 - 13729
(2021/09/08)
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- Iron-Catalyzed ?±,?-Dehydrogenation of Carbonyl Compounds
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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.
- Zhang, Xiao-Wei,Jiang, Guo-Qing,Lei, Shu-Hui,Shan, Xiang-Huan,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 1611 - 1615
(2021/03/03)
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- Ruthenium-Catalyzed Dehydrogenation Through an Intermolecular Hydrogen Atom Transfer Mechanism
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The direct dehydrogenation of alkanes is among the most efficient ways to access valuable alkene products. Although several catalysts have been designed to promote this transformation, they have unfortunately found limited applications in fine chemical synthesis. Here, we report a conceptually novel strategy for the catalytic, intermolecular dehydrogenation of alkanes using a ruthenium catalyst. The combination of a redox-active ligand and a sterically hindered aryl radical intermediate has unleashed this novel strategy. Importantly, mechanistic investigations have been performed to provide a conceptual framework for the further development of this new catalytic dehydrogenation system.
- Huang, Lin,Bismuto, Alessandro,Rath, Simon A.,Trapp, Nils,Morandi, Bill
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supporting information
p. 7290 - 7296
(2021/03/01)
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- Covalent Organic Frameworks toward Diverse Photocatalytic Aerobic Oxidations
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Photoactive two-dimensional covalent organic frameworks (2D-COFs) have become promising heterogenous photocatalysts in visible-light-driven organic transformations. Herein, a visible-light-driven selective aerobic oxidation of various small organic molecules by using 2D-COFs as the photocatalyst was developed. In this protocol, due to the remarkable photocatalytic capability of hydrazone-based 2D-COF-1 on molecular oxygen activation, a wide range of amides, quinolones, heterocyclic compounds, and sulfoxides were obtained with high efficiency and excellent functional group tolerance under very mild reaction conditions. Furthermore, benefiting from the inherent advantage of heterogenous photocatalysis, prominent sustainability and easy photocatalyst recyclability, a drug molecule (modafinil) and an oxidized mustard gas simulant (2-chloroethyl ethyl sulfoxide) were selectively and easily obtained in scale-up reactions. Mechanistic investigations were conducted using radical quenching experiments and in situ ESR spectroscopy, all corroborating the proposed role of 2D-COF-1 in photocatalytic cycle.
- Liu, Shuyang,Tian, Miao,Bu, Xiubin,Tian, Hua,Yang, Xiaobo
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supporting information
p. 7738 - 7744
(2021/05/07)
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- Zinc Stabilized Azo-anion Radical in Dehydrogenative Synthesis of N-Heterocycles. An Exclusively Ligand Centered Redox Controlled Approach
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Herein we report an exclusively ligand-centered redox controlled approach for the dehydrogenation of a variety of N-heterocycles using a Zn(II)-stabilized azo-anion radical complex as the catalyst. A simple, easy-to-prepare, and bench-stable Zn(II)-complex (1b) featuring the tridentate arylazo pincer, 2-((4-chlorophenyl)diazenyl)-1,10-phenanthroline, in the presence of zinc-dust, undergoes reduction to form the azo-anion radical species [1b]- which efficiently dehydrogenates various saturated N-heterocycles such as 1,2,3,4-tetrahydro-2-methylquinoline, 1,2,3,4-tetrahydro-isoquinoline, indoline, 2-phenyl-2,3-dihydro-1H-benzoimidazole, 2,3-dihydro-2-phenylquinazolin-4(1H)-one, and 1,2,3,4-tetrahydro-2-phenylquinazolines, among others, under air. The catalyst has further been found to be compatible with the cascade synthesis of these N-heterocycles via dehydrogenative coupling of alcohols with other suitable coupling partners under air. Mechanistic investigation reveals that the dehydrogenation reactions proceed via a one-electron hydrogen atom transfer (HAT) pathway where the zinc-stabilized azo-anion radical ligand abstracts the hydrogen atom from the organic substrate(s), and the whole catalytic cycle proceeds via the exclusive involvement of the ligand-centered redox events where the zinc acts only as the template.
- Das, Siuli,Mondal, Rakesh,Chakraborty, Gargi,Guin, Amit Kumar,Das, Abhishek,Paul, Nanda D.
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p. 7498 - 7512
(2021/06/30)
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- Visible-light-mediated organoboron-catalysed metal-free dehydrogenation of N-heterocycles using molecular oxygen
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The surge of photocatalytic transformation not only provides unprecedented synthetic methods, but also triggers the enthusiasm for more sustainable photocatalysts. On the other hand, oxygen is an ideal oxidant in terms of atom economy and environmental friendliness. However, the poor reactivity of oxygen at the ground state makes its utilization challenging. Herein, a visible-light-induced oxidative dehydrogenative process is disclosed, which uses an organoboron compound as the photocatalyst and molecular oxygen as the sole oxidant.Viathis approach, an array of N-heterocycles have been accessed under metal-free mild conditions, in good to excellent yields.
- Wei, Lanfeng,Wei, Yu,Xu, Liang,Zhang, Jinli
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supporting information
p. 4446 - 4450
(2021/06/30)
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- Monomeric vanadium oxide: A very efficient species for promoting aerobic oxidative dehydrogenation of N-heterocycles
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Monomeric active species are very interesting in heterogeneous catalysis. In this work, we proposed a method to prepare VOx-NbOy@C catalysts, which involve the one-pot hydrothermal synthesis of inorganic/organic hybrid materials containing V/Nb followed by thermal treatment under a reducing atmosphere. The prepared catalysts were characterized using different techniques, such as high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy. It was shown that monomeric VOx species were dispersed homogeneously in the catalysts. The VOx-NbOy@C catalysts displayed high performance in the aerobic oxidative dehydrogenation of N-heterocycles to aromatic heterocycles. It was demonstrated that the selectivity of reaction over the catalyst with a very small amount of V (0.07 wt%) was much higher than that over the NbOy@C, and the catalyst also exhibited excellent stability in the reaction. The detailed study indicated that monomeric VO2 species were the most effective for promoting the reaction. This journal is
- Xie, Zhenbing,Chen, Bingfeng,Zheng, Lirong,Peng, Fangfang,Liu, Huizhen,Han, Buxing
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p. 431 - 437
(2021/01/11)
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- A facile and versatile electro-reductive system for hydrodefunctionalization under ambient conditions
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A general electrochemical system for reductive hydrodefunctionalization is described, employing the inexpensive and easily available triethylamine (Et3N) as a sacrificial reductant. This protocol is characterized by facile operation, sustainable conditions, and exceptionally wide substrate scope covering the cleavage of C-halogen, N-S, N-C, O-S, O-C, C-C and C-N bonds. Notably, the selectivity and capability of reduction can be conveniently switched by simple incorporation or removal of an alcohol as a co-solvent.
- Huang, Binbin,Guo, Lin,Xia, Wujiong
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supporting information
p. 2095 - 2103
(2021/03/26)
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- N-Alkylation of Amines with Alcohols Catalyzed by Manganese(II) Chloride or Bromopentacarbonylmanganese(I)
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A manganese-catalyzed N-alkylation reaction of amines with alcohols via hydrogen autotransfer strategy has been demonstrated. The developed practical catalytic system including an inexpensive, nontoxic, commercially available MnCl2 or MnBr(CO)5 as the metal salt and triphenylphosphine as a ligand provides access to diverse aromatic, heteroaromatic, and aliphatic secondary amines in moderate-to-high yields. In addition, this operationally simple protocol is scalable to the gram level and suitable for synthesizing heterocycles such as indole and resveratrol-derived amines known to be active for Alzheimer's disease.
- Wei, Dongyue,Yang, Peng,Yu, Chuanman,Zhao, Fengkai,Wang, Yilei,Peng, Zhihua
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p. 2254 - 2263
(2021/02/26)
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- Cobalt-Catalyzed Dearomatization of Indoles via Transfer Hydrogenation to Afford Polycyclic Indolines
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A cobalt-catalyzed dearomatization of indoles via transfer hydrogenation with HBpin and H2O has been developed. This reaction offered a straightforward platform to access hexahydropyrido[1,2-a]indoles in high regio- and chemoselectivity. A preliminary reaction mechanism was proposed on the basis of deuterium-labeling experiments, and a cobalt hydride species was involved in the reaction.
- Chen, Siwei,Cai, Min,Huang, Junru,Yao, Hequan,Lin, Aijun
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supporting information
p. 2212 - 2216
(2021/04/05)
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- Exploiting a silver-bismuth hybrid material as heterogeneous noble metal catalyst for decarboxylations and decarboxylative deuterations of carboxylic acids under batch and continuous flow conditions
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Herein, we report novel catalytic methodologies for protodecarboxylations and decarboxylative deuterations of carboxylic acids utilizing a silver-containing hybrid material as a heterogeneous noble metal catalyst. After an initial batch method development, a chemically intensified continuous flow process was established in a simple packed-bed system which enabled gram-scale protodecarboxlyations without detectable structural degradation of the catalyst. The scope and applicability of the batch and flow processes were demonstrated through decarboxylations of a diverse set of aromatic carboxylic acids. Catalytic decarboxylative deuterations were achieved on the basis of the reaction conditions developed for the protodecarboxylations using D2O as a readily available deuterium source.
- ?tv?s, Sándor B.,Fül?p, Ferenc,Kónya, Zoltán,Kukovecz, ákos,Márton, András,Mészáros, Rebeka,Pálinkó, István,Szabados, Márton,Varga, Gábor
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p. 4685 - 4696
(2021/07/12)
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- Gut bacteria-derived 5-hydroxyindole is a potent stimulant of intestinal motility via its action on L-type calcium channels
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Microbial conversion of dietary or drug substrates into small bioactive molecules represents a regulatory mechanism by which the gut microbiota alters intestinal physiology. Here, we show that a wide variety of gut bacteria can metabolize the dietary supplement and antidepressant 5-hydroxytryptophan (5-HTP) to 5-hydroxyindole (5-HI) via the tryptophanase (TnaA) enzyme. Oral administration of 5-HTP results in detection of 5-HI in fecal samples of healthy volunteers with interindividual variation. The production of 5-HI is inhibited upon pH reduction in in vitro studies. When administered orally in rats, 5-HI significantly accelerates the total gut transit time (TGTT). Deciphering the underlying mechanisms of action reveals that 5-HI accelerates gut contractility via activation of L-type calcium channels located on the colonic smooth muscle cells. Moreover, 5-HI stimulation of a cell line model of intestinal enterochromaffin cells results in significant increase in serotonin production. Together, our findings support a role for bacterial metabolism in altering gut motility and lay the foundation for microbiota-targeted interventions.
- Waclawiková, Barbora,Bullock, Amber,Schwalbe, Markus,Aranzamendi, Carmen,Nelemans, Sieger A.,van Dijk, Gertjan,El Aidy, Sahar
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- A donor-acceptor complex enables the synthesis of: E -olefins from alcohols, amines and carboxylic acids
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Olefins are prevalent substrates and functionalities. The synthesis of olefins from readily available starting materials such as alcohols, amines and carboxylic acids is of great significance to address the sustainability concerns in organic synthesis. Metallaphotoredox-catalyzed defunctionalizations were reported to achieve such transformations under mild conditions. However, all these valuable strategies require a transition metal catalyst, a ligand or an expensive photocatalyst, with the challenges of controlling the region- and stereoselectivities remaining. Herein, we present a fundamentally distinct strategy enabled by electron donor-acceptor (EDA) complexes, for the selective synthesis of olefins from these simple and easily available starting materials. The conversions took place via photoactivation of the EDA complexes of the activated substrates with alkali salts, followed by hydrogen atom elimination from in situ generated alkyl radicals. This method is operationally simple and straightforward and free of photocatalysts and transition-metals, and shows high regio- and stereoselectivities.
- Chen, Kun-Quan,Shen, Jie,Wang, Zhi-Xiang,Chen, Xiang-Yu
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p. 6684 - 6690
(2021/05/31)
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- Photo-induced thiolate catalytic activation of inert Caryl-hetero bonds for radical borylation
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Substantial effort is currently being devoted to obtaining photoredox catalysts with high redox power. Yet, it remains challenging to apply the currently established methods to the activation of bonds with high bond dissociation energy and to substrates with high reduction potentials. Herein, we introduce a novel photocatalytic strategy for the activation of inert substituted arenes for aryl borylation by using thiolate as a catalyst. This catalytic system exhibits strong reducing ability and engages non-activated Caryl–F, Caryl–X, Caryl–O, Caryl–N, and Caryl–S bonds in productive radical borylation reactions, thus expanding the available aryl radical precursor scope. Despite its high reducing power, the method has a broad substrate scope and good functional-group tolerance. Spectroscopic investigations and control experiments suggest the formation of a charge-transfer complex as the key step to activate the substrates.
- K?nig, Burkhard,Wang, Hua,Wang, Shun
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supporting information
p. 1653 - 1665
(2021/06/17)
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- Method for catalytically synthesizing indole derivative by using ferrous complex
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The invention relates to a method for catalytically synthesizing an indole derivative by using a ferrous complex, which comprises the following step: by taking arylamine and acetaldehyde as raw materials and a ferrous complex containing a meta-carboboryl methylpyridine structure as a catalyst, conducting reacting at room temperature to prepare the indole derivative. Compared with the prior art, the method utilizes the ferrous complex to efficiently catalyze the reaction of arylamine and acetaldehyde at room temperature to prepare the indole derivative, the reaction condition is mild, the substrate range is wide, and the method has high catalytic activity and yield.
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Paragraph 0033-0036
(2021/07/31)
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- Indirect reduction of CO2and recycling of polymers by manganese-catalyzed transfer hydrogenation of amides, carbamates, urea derivatives, and polyurethanes
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The reduction of polar bonds, in particular carbonyl groups, is of fundamental importance in organic chemistry and biology. Herein, we report a manganese pincer complex as a versatile catalyst for the transfer hydrogenation of amides, carbamates, urea derivatives, and even polyurethanes leading to the corresponding alcohols, amines, and methanol as products. Since these compound classes can be prepared using CO2as a C1 building block the reported reaction represents an approach to the indirect reduction of CO2. Notably, these are the first examples on the reduction of carbamates and urea derivatives as well as on the C-N bond cleavage in amides by transfer hydrogenation. The general applicability of this methodology is highlighted by the successful reduction of 12 urea derivatives, 26 carbamates and 11 amides. The corresponding amines, alcohols and methanol were obtained in good to excellent yields up to 97%. Furthermore, polyurethanes were successfully converted which represents a viable strategy towards a circular economy. Based on control experiments and the observed intermediates a feasible mechanism is proposed.
- Liu, Xin,Werner, Thomas
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p. 10590 - 10597
(2021/08/20)
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- Diaryliodonium Salt-Based Synthesis of N-Alkoxyindolines and Further Insights into the Ishikawa Indole Synthesis
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A diaryliodonium salt-based strategy enabled the first systematic synthesis of rarely accessible N-alkoxyindolines. Mechanistic analyses suggested that the reaction likely involves reductive elimination of iodobenzene from iodaoxazepine via a four-membered transition state, followed by Meisenheimer rearrangement. Substrates with N-carbamate protection afforded indole in a manner similar to that of the Ishikawa indole synthesis. Preinstallation of a stannyl group as an iodonium salt precursor greatly expanded the substrate scope, and further mechanistic insights are discussed.
- Ogura, Akihiro,Shibata, Kouhei,Takao, Ken-Ichi
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p. 10067 - 10087
(2021/07/26)
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- The benzyl can be selectively removed by visible light or near visible light. Method for protecting allyl and propargyl group
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The invention provides a method for selectively removing benzyl, allyl and propargyl protecting groups by visible light or near visible light, namely a substrate containing benzyl, allyl or propargyl protecting groups. The method has the advantages of simple operation, safe and clean visible light or near visible light as excitation conditions, cheap and easily available reagents, high reaction yield, high reaction chemistry and regional selectivity, and is suitable for selective removal of benzyl, allyl and propargyl protecting groups in various substrates.
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Paragraph 0018
(2021/10/16)
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- Direct Deamination of Primary Amines via Isodiazene Intermediates
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We report here a reaction that selectively deaminates primary amines and anilines under mild conditions and with remarkable functional group tolerance including a range of pharmaceutical compounds, amino acids, amino sugars, and natural products. An anomeric amide reagent is uniquely capable of facilitating the reaction through the intermediacy of an unprecedented monosubstituted isodiazene intermediate. In addition to dramatically simplifying deamination compared to existing protocols, our approach enables strategic applications of iminium and amine-directed chemistries as traceless methods. Mechanistic and computational studies support the intermedicacy of a primary isodiazene which exhibits an unexpected divergence from previously studied secondary isodiazenes, leading to cage-escaping, free radical species that engage in a chain, hydrogen-atom transfer process involving aliphatic and diazenyl radical intermediates.
- Berger, Kathleen J.,Driscoll, Julia L.,Yuan, Mingbin,Dherange, Balu D.,Gutierrez, Osvaldo,Levin, Mark D.
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supporting information
p. 17366 - 17373
(2021/11/04)
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- Ruthenium Pincer Complex Catalyzed Selective Synthesis of C-3 Alkylated Indoles and Bisindolylmethanes Directly from Indoles and Alcohols
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Herein, we presented Ru-SNS complex that serves as a useful catalyst for C-3 alkylation of 1H-indoles with various aliphatic primary and secondary alcohols including cyclic alcohols as well as benzylic alcohols. The selective synthesis of bisindolylmethane derivatives is also achieved from the same set of indole and alcohol just by altering the reaction parameters. Furthermore, the sustainable synthesis of C-3 alkylated indoles directly from 2-(2-nitrophenyl)ethan-1-ol and alcohols catalysed by a Ru-complex via “borrowing hydrogen” strategy is reported. This protocol provides an atom-economical sustainable route to access structurally important compounds like arundine, vibrindole A and tryptamine based derivatives. (Figure presented.).
- Biswas, Nandita,Sharma, Rahul,Srimani, Dipankar
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supporting information
p. 2902 - 2910
(2020/06/03)
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- Manganese-Catalyzed Regioselective Dehydrogenative C-versus N-Alkylation Enabled by a Solvent Switch: Experiment and Computation
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The first base metal-catalyzed regioselective dehydrogenative alkylation of indolines using readily available alcohols as the alkylating reagent is reported. A single air-and moisture-stable manganese catalyst provides access to either C3-or N-alkylated indoles depending on the solvent used. Mechanistic studies indicate that the reaction takes place through a combined acceptorless dehydrogenation and hydrogen autotransfer strategy.
- Borghs, Jannik C.,Zubar, Viktoriia,Zubar, Viktoriia,Azofra, Luis Miguel,Sklyaruk, Jan,Rueping, Magnus,Rueping, Magnus
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supporting information
p. 4222 - 4227
(2020/06/04)
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- Ir-Catalyzed Reversible Acceptorless Dehydrogenation/Hydrogenation of N-Substituted and Unsubstituted Heterocycles Enabled by a Polymer-Cross-Linking Bisphosphine
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The polystyrene-cross-linking bisphosphine ligand PS-DPPBz was effective for the Ir-catalyzed reversible acceptorless dehydrogenation/hydrogenation of N-heterocycles. Notably, this protocol is applicable to the dehydrogenation of N-substituted indoline derivatives with various N-substituents with different electronic and steric natures. A reaction pathway involving oxidative addition of an N-adjacent C(sp3)-H bond to a bisphosphine-coordinated Ir(I) center is proposed for the dehydrogenation of N-substituted substrates.
- Zhang, Deliang,Iwai, Tomohiro,Sawamura, Masaya
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supporting information
p. 5240 - 5245
(2020/07/03)
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- Nickel-Catalyzed Dehydrogenation of N-Heterocycles Using Molecular Oxygen
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Herein, an efficient and selective nickel-catalyzed dehydrogenation of five- and six-membered N-heterocycles is presented. The transformation occurs in the presence of alkyl, alkoxy, chloro, free hydroxyl and primary amine, internal and terminal olefin, trifluoromethyl, and ester functional groups. Synthesis of an important ligand and the antimalarial drug quinine is demonstrated. Mechanistic studies revealed that the cyclic imine serves as the key intermediate for this stepwise transformation.
- Banerjee, Debasis,Bera, Atanu,Bera, Sourajit
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supporting information
(2020/09/02)
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- Method for catalyzing receptor-free dehydrogenation of primary amine to generate nitrile by Ru coordination compound
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The invention discloses a method for catalyzing receptor-free dehydrogenation of primary amine to generate nitrile by a Ru coordination compound. The method comprises: adding a Ru coordination compound, an alkali, a primary amine and an organic solvent into a reaction test tube according to a mol ratio of 1:100:(100-500):1000-3000, and carrying out a stirring reaction under the condition of 80 to120 DEG C; and when gas chromatography monitors that the raw materials completely disappear, stopping the reaction, collecting the reaction solution, centrifuging the reaction solution, taking the supernatant, extracting with dichloromethane, merging the organic phases, drying, filtering, evaporating the organic solvent under reduced pressure to obtain a filtrate, and carrying out column chromatography purification on the filtrate to obtain the target product nitrile. According to the invention, the catalyst is good in activity, single in catalytic system, good in product selectivity, simple in subsequent treatment and good in system universality after the reaction is finished, has a good catalytic effect on various aryl, alkyl and heteroaryl substituted primary amines, and also has a gooddehydrogenation performance on secondary amines.
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Paragraph 0034-0039; 0298-0303
(2020/09/16)
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- Visible-Light-Promoted Efficient Aerobic Dehydrogenation of N-Heterocycles by a Tiny Organic Semiconductor Under Ambient Conditions
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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.
- Su, Chenliang,Yu, Kunyi,Zhang, Hanjie,Zhu, Yongfa
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supporting information
p. 1956 - 1960
(2020/04/10)
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- Reusable, homogeneous water soluble photoredox catalyzed oxidative dehydrogenation of N-heterocycles in a biphasic system: Application to the synthesis of biologically active natural products
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Herein, a simple and efficient method for the oxidative dehydrogenation (ODH) of tetrahydro-β-carbolines, indolines and tetrahydro-(iso)quinolines is described using a reusable, homogeneous cobalt-phthalocyanine photoredox catalyst in a biphasic medium. A biphasic system offers an advantage of easy separation of the product and an efficient reusability of the homogeneous photoredox catalyst. Also, the current system significantly helps to overcome the solubility issue of the substrate and catalyst at room temperature. Its potential applications to organic transformations are demonstrated by the synthesis of various biologically active N-heterocycles such as indoles, (iso)quinolines and β-carbolines and natural products such as eudistomin U, norharmane, and harmane and precursors to perlolyrine and flazin. Without isolation and purification, the catalyst solution can be reused up to 5 times with almost comparable reactivity. Furthermore, the efficiency of the reaction was demonstrated on a gram scale. To the best of our knowledge, this is the first report on ODH reactions using a non noble, reusable and homogeneous cobalt photoredox catalyst under environmentally friendly conditions.
- Abinaya, R.,Baskar, B.,Mariappan, M.,Prasanth, Arun,Sridhar, R.,Srinath, S.
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p. 2575 - 2587
(2020/05/13)
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- Aerobic Dehydrogenation of N-Heterocycles with Grubbs Catalyst: Its Application to Assisted-Tandem Catalysis to Construct N-Containing Fused Heteroarenes
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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.
- Kawauchi, Daichi,Noda, Kenta,Komatsu, Yoshiyuki,Yoshida, Kei,Ueda, Hirofumi,Tokuyama, Hidetoshi
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supporting information
p. 15793 - 15798
(2020/10/12)
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- Hydrogenation or Dehydrogenation of N-Containing Heterocycles Catalyzed by a Single Manganese Complex
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A highly chemoselective base-metal catalyzed hydrogenation and acceptorless dehydrogenation of N-heterocycles is presented. A well-defined Mn complex operates at low catalyst loading (as low as 2 mol %) and under mild reaction conditions. The described catalytic system tolerates various functional groups, and the corresponding reduced heterocycles can be obtained in high yields. Experimental studies indicate a metal-ligand cooperative catalysis mechanism.
- Borghs, Jannik C.,Rueping, Magnus,Zubar, Viktoriia
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supporting information
(2020/05/19)
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- Acceptorless dehydrogenation of amines and alcohols using simple ruthenium chloride
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A highly efficient, economic and environmental friendly catalyst system has been developed for the dehydrogenation of alcohols and amines using simple RuCl3·nH2O and N-benzylhexamethylenetetramine. The in situ catalyst system efficiently oxidized the primary and secondary amines and secondary alcohols into nitrile, imine and ketone products, respectively in moderate to excellent yields. The developed catalyst system was also found to be efficient for the dehydrogenation of N-heterocyles. A detailed mechanism study revealed the first example of N-benzylhexamethylenetetramine (HMTA-Bz) being simultaneously acting as base, reducing agent and hydride source to generate the [Ru(II)(H)2] species as the active catalyst. The mechanism studies also revealed both the alcohol and amine oxidation involves dehydrogenative pathway with the evolution of hydrogen as the only by-product. The developed catalyst system also provides possible platform for the release of hydrogen from liquid organic hydrogen carriers (LOHCs).
- Barteja, Parul,Devi, Preeti,Kannan, Muthukumar,Muthaiah, Senthilkumar
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- Rh/TiO2-Photocatalyzed Acceptorless Dehydrogenation of N-Heterocycles upon Visible-Light Illumination
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TiO2 is an effective and extensively employed photocatalyst, but its practical use in visible-light-mediated organic synthesis is mainly hindered by its wide band gap energy. Herein, we have discovered that Rh-photodeposited TiO2 nanoparticles selectively dehydrogenate N-heterocyclic amines with the concomitant generation of molecular hydrogen gas in an inert atmosphere under visible light (λmax = 453 nm) illumination at room temperature. Initially, a visible-light-sensitive surface complex is formed between the N-heterocycle and TiO2. The acceptorless dehydrogenation of N-heterocycles is initiated by direct electron transfer from the HOMO energy level of the amine via the conduction band of TiO2 to the Rh nanoparticle. The reaction condition was optimized by examining different photodeposited noble metals on the surface of TiO2 and solvents, finding that Rh0 is the most efficient cocatalyst, and 2-propanol is the optimal solvent. Structurally diverse N-heterocycles such as tetrahydroquinolines, tetrahydroisoquinolines, indolines, and others bearing electron-deficient as well as electron-rich substituents underwent the dehydrogenation in good to excellent yields. The amount of released hydrogen gas evinces that only the N-heterocyclic amines are oxidized rather than the dispersant. This developed method demonstrates how UV-active TiO2 can be employed in visible-light-induced synthetic dehydrogenation of amines and simultaneous hydrogen storage applications.
- Bahnemann, Detlef W.,Balayeva, Narmina O.,Dillert, Ralf,Mamiyev, Zamin,Zheng, Nan
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p. 5542 - 5553
(2020/08/25)
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- Monoamine Oxidase (MAO-N) Biocatalyzed Synthesis of Indoles from Indolines Prepared via Photocatalytic Cyclization/Arylative Dearomatization
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The biocatalytic aromatization of indolines into indole derivatives exploiting monoamine oxidase (MAO-N) enzymes is presented. Indoline substrates were prepared via photocatalytic cyclization of arylaniline precursors or via arylative dearomatization of unsubstituted indoles and in turn chemoselectively aromatized by the MAO-N D11 whole cell biocatalyst. Computational docking studies of the indoline substrates in the MAO-N D11 catalytic site allowed for the rationalization of the biocatalytic mechanism and experimental results of the biotransformation. This methodology represents an efficient example of biocatalytic synthesis of indole derivatives and offers a facile approach to access these aromatic heterocycles under mild reaction conditions.
- Black, Gary W.,Brancale, Andrea,Castagnolo, Daniele,Colonna, Serena,Ferla, Salvatore,Masci, Domiziana,Turner, Nicholas J.,Varricchio, Carmine,Zhao, Fei
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p. 6414 - 6421
(2020/07/09)
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- Flavin/I2-Catalyzed Aerobic Oxidative C–H Sulfenylation of Aryl-Fused Cyclic Amines
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We report an aerobic oxidative C–H sulfenylation of aryl-fused cyclic amines with various thiols catalyzed by flavin/I2 for the first time. While flavin I catalyzed the C–H sulfenylation of indolines to afford 3-sulfenylindoles, flavin II enabl
- Jiang, Xinpeng,Zhao, Zongchen,Shen, Zhifeng,Chen, Keda,Fang, Liyun,Yu, Chuanming
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supporting information
p. 3889 - 3895
(2020/06/01)
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- Development of Pd(OAc)2-catalyzed tandem oxidation of C[sbnd]N, C[sbnd]C, and C(sp3)–H bonds: Concise synthesis of 1-aroylisoquinoline, oxoaporphine, and 8-oxyprotoberberine alkaloids
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A catalytic tandem oxidation of C[sbnd]N, C[sbnd]C, and C(sp3)–H bonds is developed. This tandem oxidation is applied to two-step total syntheses of papaveraldine and pulcheotine A. Additionally, the total synthesis of liriodenine is achieved in six steps from homopiperonyl alcohol and 2-bromophenylacetonitrile by applying this catalytic tandem oxidation. Moreover, the direct conversion of xylopinine to 8-oxypseudopalmatine in a 76% yield demonstrates the versatility of this catalytic reaction.
- Nishimoto, Saeko,Nakahashi, Hiromichi,Toyota, Masahiro
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- MnOx/catechol/H2O: A cooperative catalytic system for aerobic oxidative dehydrogenation of N-heterocycles at room temperature
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Amorphous manganese oxide doped by Na+ ion (Na-AMO) was successfully prepared and found to be an efficient heterogeneous catalyst in aerobic oxidative dehydrogenation of N-heterocycles, cooperate with catechol. Na-AMO was fully characterized by XRD, XPS BET H2-TPR, CO2-TPD FT-IR, TEM, SEM and had rich amounts of surface absorbed active oxygen species which are responsible for superior catalytic performance. The synergistic interaction between Na-AMO and catechol makes catalytic system efficient and tolerant, which offers various N-heterocycles in good to excellent yields under mild conditions.
- Tang, Tao,Bi, Xiuru,Meng, Xu,Chen, Gexin,Gou, Mingxia,Liu, Xiang,Zhao, Peiqing
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- Catalytic Aerobic Dehydrogenatin of N-Heterocycles by N-Hydoxyphthalimide
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Catalytic methods for the aerobic dehydrogenation of N-heterocycles are reported. In most cases, indoles are accessed efficiently from indolines using catalytic N-hydroxyphthalimide (NHPI) as the sole additive under air. Further studies revealed an improved catalytic system of NHPI and copper for the preparation of other heteroaromatics, for example quinolines. (Figure presented.).
- Chen, Weidong,Tang, Hao,Wang, Weilin,Fu, Qiang,Luo, Junfei
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supporting information
p. 3905 - 3911
(2020/08/10)
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- Dehydrogenation and α-functionalization of secondary amines by visible-light-mediated catalysis
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A visible-light-mediated process for dehydrogenation of amines has been described. The given protocol showed a broad substrate scope, mild reaction conditions and excellent results without the requirement of tedious purification. This process can be applied in one-pot functionalization of secondary amines with various nucleophiles through the cooperation of visible-light and Lewis acid catalysis, leading to the structurally varied essential components of biologically active molecules. In addition, Stern-Volmer studies and quenching experiments revealed the role of a catalyst and led to the proposed mechanism of this transformation.
- Bujok, Robert,Morawska, Paulina,Pawlowski, Robert,Stanek, Filip,Stodulski, Maciej
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supporting information
p. 2103 - 2112
(2020/03/27)
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- DMSO/t-BuONa/O2-Mediated Aerobic Dehydrogenation of Saturated N-Heterocycles
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Aromatic N-heterocycles such as quinolines, isoquinolines, and indolines are synthesized via sodium tert-butoxide-promoted oxidative dehydrogenation of the saturated heterocycles in DMSO solution. This reaction proceeds under mild reaction conditions and has a good functional group tolerance. Mechanistic studies suggest a radical pathway involving hydrogen abstraction of dimsyl radicals from the N-H bond or α-C-H of the substrates and subsequent oxidation of the nitrogen or α-aminoalkyl radicals.
- Cai, Hu,Tan, Wei,Xie, Yongfa,Yang, Ruchun,Yue, Shusheng
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p. 7501 - 7509
(2020/07/07)
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- Applications of rare earth silicon amination material as catalyst in preparation of indole or indole derivative
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The invention belongs to the technical field of chemical engineering, and specially provides applications of a rare earth silicon amination material as a catalyst in preparation of indole or an indolederivative, wherein the reaction raw materials comprise a compound I, the general formula of the compound I is shown in the specification, R is hydrogen, methyl, chlorine, fluorine, bromine or methoxyl, the rare earth silicon amination material M[N(SiMe3)2]3 is a catalyst, and M is a rare earth element. According to the invention, the indole or the indole derivative is prepared by taking the rareearth silicon amination material as the catalyst and taking the compound I and pinacol boron as the raw materials; the method is simple and convenient to operate and high in reaction selectivity; andthe synthesized indole derivative is good in product quality and high in yield.
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Paragraph 0038-0042; 0073-0094
(2020/03/03)
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