- Photoredox-Catalyzed Dehydrogenative Csp3-Csp2Cross-Coupling of Alkylarenes to Aldehydes in Flow
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Executing photoredox reactions in flow offers solutions to frequently encountered issues regarding reproducibility, reaction time, and scale-up. Here, we report the transfer of a photoredox-catalyzed benzylic coupling of alkylarenes to aldehydes to a flow chemistry setting leading to improvements in terms of higher concentration, shorter residence times, better yields, ease of catalyst preparation, and enhanced substrate scope. Its applicability has been demonstrated by a multi-gram-scale reaction using high-power light-emitting diodes (LEDs), late-stage functionalization of selected active pharmaceutical ingredients (APIs), and also a photocatalyst recycling method.
- Griffiths, Oliver M.,Esteves, Henrique A.,Chen, Yiding,Sowa, Karin,May, Oliver S.,Morse, Peter,Blakemore, David C.,Ley, Steven V.
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supporting information
p. 13559 - 13571
(2021/10/01)
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- Catalytic Asymmetric (3 + 3) Cycloaddition of Oxyallyl Zwitterions with α-Diazomethylphosphonates
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The unique structure of oxyallyls represents a significant challenge for their catalytic asymmetric applications. Herein, an unprecedented chiral imidodiphosphoric acid-catalytic enantioselective (3 + 3) cycloaddition between oxyallyl zwitterions generate
- Liu, Yan,Peng, Xian,Peng, Yungui,She, Rui,Zhou, Xin
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supporting information
p. 7295 - 7300
(2021/10/01)
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- Tetraaryl Cyclopentadienones: Experimental and Theoretical Insights into Negative Solvatochromism and Electrochemistry
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The synthesis of a series of tetraaryl cyclopentadienones comprising different substitution patterns is reported. Their photophysical and electrochemical properties are investigated by UV/Vis spectroscopy and cyclic voltammetry as well as by supporting quantum chemical simulations and reveal a distinct effect of substituents on the redox behavior of the molecules as well as the absorption properties of this class of compounds. While electrochemical data display a shift in reduction potential of up to 200 mV between the differently substituted cyclopentadienones, their photophysical investigations in differently polar solvents suggest a negative solvatochromic effect, although protic solvents induce a bathochromic shift. Crystal structure analyses of some derivatives confirm similarity with related cyclopentadienones while providing insight into intermolecular C–H···O and C–H···π interactions in the solid state.
- Meitinger, Nicolas,Mengele, Alexander K.,Witas, Kamil,Kupfer, Stephan,Rau, Sven,Nauroozi, Djawed
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p. 6555 - 6562
(2020/10/02)
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- Direct α-Benzylation of Methyl Enol Ethers with Activated Benzyl Alcohols: Its Rearrangement and Access to (±)-Tetrahydronyasol, Propterol A, and 1,3-Diarylpropane
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Herein, we report a one-pot Lewis acid mediated synthesis of bi- and triarylpropanal derivatives and their corresponding isomeric ketones from aromatic enol ethers. This transformation takes place via nucleophilic attack of enol ethers to electron-rich be
- Jena, Tapan Kumar,Khan, Faiz Ahmed
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p. 14270 - 14280
(2019/10/17)
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- Generation and Reactivity Studies of Diarylmethyl Radical Pairs in Crystalline Tetraarylacetones via Laser Flash Photolysis Using Nanocrystalline Suspensions
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The nanosecond electronic spectra and kinetics of the radical pairs from various crystalline tetraarylacetones were obtained using transmission laser flash photolysis methods by taking advantage of aqueous nanocrystalline suspensions in the presence of su
- Park, Jin H.,Hughs, Melissa,Chung, Tim S.,Ayitou, A. Jean-Luc,Breslin, Vanessa M.,Garcia-Garibay, Miguel A.
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supporting information
p. 13312 - 13317
(2017/10/05)
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- Synthesis of acyclic ketones by catalytic, bidirectional homologation of formaldehyde with nonstabilized diazoalkanes. Application of a chiral diazomethyl(pyrrolidine) in total syntheses of erythroxylon alkaloids
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This work offers a catalytic approach to convergent ketone assembly based upon formal and tandem C-H insertion of diazoalkanes in the presence of limiting amounts of monomeric formaldehyde, which is easily generated as a gas by thermolysis of the inexpensive and abundant paraformaldehyde (~30 USD/kg). The method forms di-, tri-, and even tetrasubstituted acetones with high efficiency, and it has streamlined a synthesis of (-)-dihydrocuscohygrine in which the absolute stereochemistry of a proline-based starting material is preserved. Assisted by the advent of new protocols for hydrazone oxidation, we also provide full details on handling non-carbonyl-stabilized diazo compounds.
- Wommack, Andrew J.,Kingsbury, Jason S.
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p. 10573 - 10587
(2013/11/19)
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- Spatially controlled surface immobilization of nonmodified peptides
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A phencyclone derivative is used to achieve light-controlled immobilization of peptides possessing only natural amino acids. The photoactive precursor (blue in picture) is formed in a Diels-Alder reaction and can undergo light-triggered ring-opening reactions with amines. Successful surface patterning with a genuine c(RGDfK) peptide (green) is evidenced by imaging time-of-flight secondary-ion mass spectrometry (ToF-SIMS). Copyright
- Pauloehrl, Thomas,Welle, Alexander,Bruns, Michael,Linkert, Katharina,B?rner, Hans G.,Bastmeyer, Martin,Delaittre, Guillaume,Barner-Kowollik, Christopher
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supporting information
p. 9714 - 9718
(2013/09/23)
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- Efficient synthesis of substituted polyarylphthalimides via cycloaddition of cyclopentadienones with 2-bromomaleimide
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Functionalized tetraarylphthalimides or diarylphthalimides fused with an acenaphthene moiety have been prepared in one step from 2-bromomaleimide and tetraarylcyclopentadienones (tetracyclones) or 7,9-diaryl-8H- cyclopentacenaphthylene-8-ones (acecyclones
- Vanel, Rémi,Berthiol, Florian,Bessières, Bernard,Einhorn, Cathy,Einhorn, Jacques
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p. 1293 - 1295
(2011/07/07)
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- Synthesis and serotonin transporter activity of 1,3-bis(aryl)-2-nitro-1- propenes as a new class of anticancer agents
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Structural derivatives of 4-MTA, an illegal amphetamine analogue have been previously shown to have anticancer effects in vitro. In this study we report the synthesis of a series of novel 1,3-bis(aryl)-2-nitro-1-propene derivatives related in structure to 4-MTA. A number of these compounds containing a classic nitrostyrene structure are shown to have antiproliferative activities in vitro in a range of malignant cell lines, particularly against Burkitt's lymphoma derived cell lines, whilst having no effect on 'normal' peripheral blood mononuclear cells. Such effects appear to be independent of the serotonin transporter, a high affinity target for amphetamines and independent of protein tyrosine phosphatases and tubulin dynamics both of which have been previously associated with nitrostyrene-induced cell death. We demonstrate that a number of these compounds induce caspase activation, PARP cleavage, chromatin condensation and membrane blebbing in a Burkitt's lymphoma derived cell line, consistent with these compounds inducing apoptosis in vitro. Although no specific target has yet been identified for the action of these compounds, the cell death elicited is potent, selective and worthy of further investigation.
- McNamara, Yvonne M.,Cloonan, Suzanne M.,Knox, Andrew J.S.,Keating, John J.,Butler, Stephen G.,Peters, Günther H.,Meegan, Mary J.,Williams, D. Clive
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p. 1328 - 1348
(2011/04/17)
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- Tuning of the electronic properties of a cyclopentadienylruthenium catalyst to match racemization of electron-rich and electron-deficient alcohols
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The synthesis of a new series of cyclopentadienylruthenium catalysts with varying electronic properties and their application in racemization of secondary alcohols are described. These racemizations involve two key steps: 1) β-hydride elimination (dehydrogenation) and 2) re-addition of the hydride to the intermediate ketone. The results obtained confirm our previous theory that the electronic properties of the substrate determine which of these two steps is rate determining. For an electron-deficient alcohol the rate-determining step is the β-hydride elimination (dehydrogenation), whereas for an electron-rich alcohol the re-addition of the hydride becomes the rate-determining step. By matching the electronic properties of the catalyst with the electronic properties of the alcohol, we have now shown that a dramatic increase in racemization rate can be obtained. For example, electron-deficient alcohol 15 racemized 30 times faster with electron-deficient catalyst 6 than with the unmodified standard catalyst 4. The application of these protocols will extend the scope of cyclopentadienylruthenium catalysts in racemization and dynamic kinetic resolution. Copyright
- Verho, Oscar,Johnston, Eric V.,Karlsson, Erik,Baeckvall, Jan-E.
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experimental part
p. 11216 - 11222
(2011/11/05)
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- Tuning the singlet-triplet gap in metal-free phosphorescent π-conjugated polymers
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Glow in the dark: A tunable singlet-triplet exchange gap arises in optically active conjugated polymers that exhibit both strong fluorescence from the singlet state and pronounced phosphorescence from triplet excitations (see picture). The polymers were incorporated into organic light-emitting diodes (OLEDs).
- Chaudhuri, Debangshu,Wettach, Henning,Van Schooten, Kipp J.,Liu, Su,Sigmund, Eva,Hoeger, Sigurd,Lupton, John M.
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supporting information; experimental part
p. 7714 - 7717
(2010/12/25)
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- Solid state conformational preferences of a flexible molecular backbone derived from acetone: Dependence on electron donating/withdrawing ability of substitutions
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Conformational preferences, crystal packing, and intermolecular interactions can play a pivotal role in solid state reactions, and in particular for bis(phenyl)acetones, these factors are known to determine the rate of the photodecarbonylation process. In
- Varughese, Sunil,Draper, Sylvia M.
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experimental part
p. 2298 - 2305
(2011/11/07)
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- Predicting the UV-vis spectra of tetraarylcyclopentadienones: Using DFT molecular orbital energies to model electronic transitions of organic materials
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(Chemical Equation Presented) Tetraphenylcyclopentadienone, due to its intrinsically low HOMO-LUMO gap, has been suggested as a valuable repeat unit in conducting polymers for nanoscale electronics. The HOMO and LUMO of tetraphenylcyclopentadienone appear
- Potter, Robert G.,Hughes, Thomas S.
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p. 2995 - 3004
(2008/09/19)
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- Hydrogen-bond quenching of photodecarbonylation in the solid state and recovery of reactivity by co-crystallization
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Intermolecular H-bonding between C=O (ketone) and HO (4′- hydroxyphenyl) quenches photodecarbonylation of 2,2,4,4-tetramethyl-1,3- di(4′-hydroxyphenyl)acetone 1 in the crystalline solid state, its reactivity is recovered by co-crystallization with the small organic molecule 4,4′-bicyclohexanone. The Royal Society of Chemistry.
- Zhang, Jing,Gembicky, Milan,Messerschmidt, Marc,Coppens, Philip
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p. 2399 - 2401
(2008/02/10)
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- Synthesis of heterosubstituted hexaarylbenzenes via asymmetric carbonylative couplings of benzyl halides
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Asymmetric carbonylative couplings of benzyl halldes have been shown to give heterosubstituted 1,3-diarylacetones In moderate to high yields. These asymmetric ketones were converted via Knoevenagel condensations to tetraarylcyclopentadienones, and further
- Potter, Robert G.,Hughes, Thomas S.
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p. 1187 - 1190
(2008/01/04)
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- Fast DKR of amines using isopropyl 2-methoxyacetate as acyl donor
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The dynamic kinetic resolution (DKR) of various primary amine substrates was performed using a modified version of the Baeckvall system. A single equivalent of isopropyl 2-methoxyacetate was used as acyl donor in combination with p-MeO Shvo complex as the racemization catalyst and Novozym 435 as the acylation catalyst. A reaction temperature of 100°C was employed to ensure a high racemization rate. Adding 2,4-dimethyl-3-pentanol (DMP) as hydrogen donor at a concentration of 0.5 M successfully suppressed side product formation. Under these modified DKR conditions, complete conversion was observed for most substrates within 26 h showing both high ee values and good chemoselectivity, whereas the original system required a reaction time of 72 h. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Veld, Martijn A. J.,Hult, Karl,Palmans, Anja R. A.,Meijer
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p. 5416 - 5421
(2008/03/18)
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- Dakin-West synthesis of β-aryl ketones
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Triethylamine and 1-methylimidazole were found to be selective catalysts for the Dakin-West synthesis of diaryl ketones and aryl methyl ketones, respectively. In the 1-methylimidazole-catalyzed reaction, catalysis is due to the simultaneous formation of both an effective acylating agent, 1-acyl-3-methylimidazolium, and a base, carboxylate anion. Hydrocinnamic acid, a compound previously reported to be unreactive under Dakin-West conditions, forms 4-phenyl-2-butanone when the reaction is catalyzed by 1-methylimidazole.
- Tran, Khanh-Van,Bickar, David
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p. 6640 - 6643
(2007/10/03)
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- A novel synthesis of bisbenzyl ketones by DCC induced condensation of phenylacetlc acid
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1,3-Dicyclohexylcarbodiimide (DCC) has been found to effect condensation of two molecules of phenylacetic acids in the presence of dimethylaminopyridine leading to the formation of bisbenzyl ketones.
- Bhandari, Sumita,Ray, Suprabhat
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p. 765 - 771
(2007/10/03)
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- Synthesis, chemical transformation and antimicrobial activity of a novel class of nitroolefins: 1,3-diaryl-2-nitroprop-1-enes
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The synthesis of novel, biologically active 1,3-diaryl-2- nitroprop-1-enes (4) is reported. The synthesis involves condensation between aromatic aldehydes (1) and β-aryl nitroethanes (3). The chemical transformation of the nitro group in diaryl nitropropenes to a carbonyl function has resulted in a new route to the synthesis of an α-hydroxy analog (7c) of a naturally occurring 3,3',4,4'-tetramethoxy chalcone. The antimicrobial activity of the 1,3-diaryl-2-nitroprop-1-enes (4a- j) was tested against three gram positive bacteria, two gram negative bacteria and two fungi. These compounds exhibited broad spectrum antimicrobial activity.
- Kodukulla,Trivedi,Vora,Mathur
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p. 819 - 832
(2007/10/02)
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- 76. Large Water-Soluble Cyclophanes with Convergent Intracavity Functionality
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New tricyclic spacers, readily available trough fourfold Mannich reaction of substituted dibenzyl ketones, were introduced into a series of ten H2O-soluble cyclophanes with spacious preorganized cavity binding sites.These spacers provide H2O-solubility with amine or crown-ether functionality remote from the cyclophane cavity while directing functional groups such as keto or OH groups in a precise geometrical array inside the cavity.The cyclophanes were designed to include organic substrates via a combination of apolar and specific polar functionalgroup interactions.The X-ray crystal-structure analysis of the tritopic receptor 18 with one potential neutralmolecule and two cation-binding sites showed a large rectangular open cavity with dimensions of roughly 9 x 14 Angstroem and a spacing of 9.7 Angstroem between the O-atoms of two convergent C=O groups.Despite the binding-site preorganization, cyclophanes incorporating two of the new spacers did not show any substrate binding in aqueous solutions.The failure of these systems to function as receptors is mainly due to steric hindrance to important cyclophane aromatic ring-guest interactions.Also, the favorable solvation of the intracavity functionality may prevent the formation of complexes.Hybrid receptors constructed from the novel spacers and diphenylmethane units were found to bind flat aromatic substrates as well as bulky paracyclophanes.The observed large differences in stability (ΔΔGo > 2 kcal mol-1) of the complexes formed by three structurally closely related hybrid receptors with convergent C=O, OH, or CH2 groups and 6-hydroxynaphthalene-2-carbonitrile as guest can be explained by a strong solvation effect of the convergent functional groups on apolar inclusion complexation.
- Diederich, Francois,Carcanague, Daniel R.
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p. 800 - 818
(2007/10/02)
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- A Study of Substituent Effects on Hydrogen-to-Arene Nonbonded Interactions
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The polycyclic aromatic hydrocarbon 9,14-diphenylbenzotriphenylene is strongly twisted due to nonbonded interactions between hydrogen atoms on the polycyclic nucleus and the ? systems of the phenyl groups.Ten derivatives of 9,14-diphenylbenzotriphen
- L'Esperance, Robert P.,Engen, Donna Van,Dayal, Rajeev,Pascal, Robert A.
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p. 688 - 694
(2007/10/02)
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- Homoaromaticity in Anions: The Effect of Electron Donor Groups
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Base-catalysed exchange of 2,4-di-p-anisoylbicycloocta-2,6-diene (10) proceeds faster than that of 2,4-di-p-anisoylbicyclooct-2-ene (13) indicating the significance of homoaromaticity in anions and the utility of the electron-demand tool to detect such interactions.
- Tuncay, Atilla,Carroll, Margaret A.,Labeots, Laura A.,Pawlak, Joe M.
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p. 1590 - 1592
(2007/10/02)
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- PROPTEROL: A 1,3-DIARYLPROPAN-2-OL FROM PTEROCARPUS MARSUPIUM
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The structure of propterol, an extractive of the heartwood of Pterocarpus marsupium, has been established to be 1,3-bis(4-hydroxyphenyl)propan-2-ol, on the basis of its spectral data and Jones oxidation of its dimethyl ether to known 1,3-bis(4-methoxyphen
- Subba Rao, A.V.,Mathew, James,Sankaram, A. V. B.
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p. 897 - 898
(2007/10/02)
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- Self-Termination and Electronic Spectra of Substituted Benzyl Radicals in Solution
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Several substituted benzyl radicals have been generated in liquid cyclohexane by the photolysis of symmetrically substituted dibenzyl ketones.The rate constants for self-termination to substituted bibenzyls, and absorption spectra of the transient radicals, have been measured by optical modulation spectroscopy.The termination rates are generally well described by the von Smoluchowski equation with a spin factor of 1/4.Deviations are discussed in terms of steric retardation and the unreliability of the estimated reaction diameters of radicals with bulky substituent groups.Absorption spectra of the three monomethyl-, the three monochloro-, two dichloro-, and the three monomethoxybenzyl radicals demonstrate the influence of the substituents on the energy levels of the benzyl system.
- Claridge, Rodney F. C.,Fischer, Hanns
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p. 1960 - 1967
(2007/10/02)
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- Reactions of Diphenylcyclopropenone and Tetracyclones with Potassium Superoxide
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Reactions of diphenylcyclopropenone and various tetracyclones with potassium superoxide are reported.
- Neckers, Douglas C.,Hauck, Gerhard
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p. 4691 - 4695
(2007/10/02)
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- Polycyclic Aromatic Compounds: Part V - A Convenient Synthesis of a New Class of Bis-ethers
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The dienophilic character of bis-acetylenic ether (IV) is studied and a new series of bis-ethers (VI, VIII and IX) are obtained by the condensation of IV with various cyclopentadienones.
- Bandyopadhyay, T. K.,Bhattacharya, A. J.
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p. 620 - 622
(2007/10/02)
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