- Generating carbyne equivalents with photoredox catalysis
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Carbon has the unique ability to bind four atoms and form stable tetravalent structures that are prevalent in nature. The lack of one or two valences leads to a set of species - carbocations, carbanions, radicals and carbenes - that is fundamental to our understanding of chemical reactivity. In contrast, the carbyne - a monovalent carbon with three non-bonded electrons - is a relatively unexplored reactive intermediate; the design of reactions involving a carbyne is limited by challenges associated with controlling its extreme reactivity and the lack of efficient sources. Given the innate ability of carbynes to form three new covalent bonds sequentially, we anticipated that a catalytic method of generating carbynes or related stabilized species would allow what we term an € assembly point' disconnection approach for the construction of chiral centres. Here we describe a catalytic strategy that generates diazomethyl radicals as direct equivalents of carbyne species using visible-light photoredox catalysis. The ability of these carbyne equivalents to induce site-selective carbon-hydrogen bond cleavage in aromatic rings enables a useful diazomethylation reaction, which underpins sequencing control for the late-stage assembly-point functionalization of medically relevant agents. Our strategy provides an efficient route to libraries of potentially bioactive molecules through the installation of tailored chiral centres at carbon-hydrogen bonds, while complementing current translational late-stage functionalization processes. Furthermore, we exploit the dual radical and carbene character of the generated carbyne equivalent in the direct transformation of abundant chemical feedstocks into valuable chiral molecules.
- Wang, Zhaofeng,Herraiz, Ana G.,Del Hoyo, Ana M.,Suero, Marcos G.
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- A 2- fluoro fumaric acid ester (formula I) and its preparation method and application
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The invention discloses 2-fuloro fumarate (formula I) and a preparation method thereof. Experiments show that: the kinds of compounds are capable of effectively inhibiting NF-kB transcriptional activity introduced by TNF-alpha, and further are capable of treating diseases introduced by NF-kB, such as psoriasis, multiple sclerosis, arthritis, eye inflammation or allergy, asthma and lupus erythematosus, and can be used as an immunosuppressant for organ transplantation.
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Paragraph 0045
(2017/01/23)
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- Propeller-Shaped D3h-Symmetric Macrocycles with Three 1,8-Diazaanthracene Blades as Building Blocks for Photochemically Induced Growth Reactions
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The efficient synthesis of new D3h-symmetric propeller-shaped, double-decker compounds with three vertically standing diazaanthracene units arranged so as to allow for photochemically induced intermolecular growth reaction by [4+4] cycloaddition is presented. The propellers bear alkyl chains of four different lengths (ethyl, propyl, hexyl, dodecyl) to have flexibility in creating ordered arrays by packing them into single crystals, onto solid substrates or into mesophases. All propellers are obtained in only six steps and on a 50-200 mg scale. The sequence passes through the ditriflated 1,8-diazaanthracene derivatives 6 which are a very versatile building block for many purposes and were therefore synthesized on a 30 g scale. A new class of propeller-shaped macrocycles is accessible via a six-step procedure with overall yields ranging from 6-16%. These cyclophanes are equipped with 1,8-diazaanthracene units and are designed for photochemical growth reactions in two dimensions.
- Servalli, Marco,Gyr, Luzia,Sakamoto, Junji,Schlüter, A. Dieter
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supporting information
p. 4519 - 4523
(2015/07/27)
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- Molecular structures and preferred conformations of stabilized keto diester phosphonium ylides
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Triphenylphosphonium ylidic keto diesters with a nonylidic ester group, Ph3PC(CO2CH2CH3)COCO 2CH2CH3, 1, and Ph3PC(CO 2CH2CH3)COCH2CO2CH 2CH3, 2, have the keto group syn and the ylidic ester acyl group anti to phosphorus. Conformation of 2 is assigned by X-ray crystallography, while conformations of 1 and 2 are based on 1H and 13C NMR spectroscopy, and comparisons of acyl stretching frequencies with predicted values from HF and DFT methods. Thermolyses of 1 and 2 gave the expected acetylene derivatives in high yield, consistent with the syn keto conformation and in agreement with earlier observations of thermolyses of stabilized phosphonium ylides. Results from the X-ray spectrum of 2 confirm the proposed structure.
- Casta?eda, Fernando,Silva, Paul,Teresa Garland,Shirazi, Ata,Bunton, Clifford A.
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experimental part
p. 284 - 291
(2011/12/13)
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- N-heterocyclic carbenes of indazole: Ring enlargement reactions by α-halo ketones and dehalogenations of vicinal dihalides
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On decarboxylation, 1,2-dimethylindazolium-3-carboxylate forms the N-heterocyclic carbene, 1,2-dimethylindazol-3-ylidene, which deprotonates α-halo ketones. The resulting indazolium salt and the corresponding enolate form 1:1 adducts which undergo a ring enlargement to cinnolines. Reaction with 2-bromo-2,3-dihydro-1H-inden-1-one gives a 4- hydroxyspiro[cinnoline-3,2′-inden]-1′-one by ring enlargement reaction (X-ray crystal structure analysis). Vicinal dibromides undergo debromination under these conditions to give alkenes, and substrates with 1,2-dibromoethene partial structure give acetylenes. As 3-bromoindazole is found as the second product of this reaction, an E1cb mechanism, initiated by Br+ abstraction by the N-heterocyclic carbene of indazole, is suggested. Georg Thieme Verlag Stuttgart.
- Schmidt, Andreas,Snovydovych, Bohdan,Gjikaj, Mimoza
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experimental part
p. 2798 - 2804
(2009/04/05)
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- Flash Vacuum Pyrolysis of Stabilized Phosphorous Ylides. Part 5. Selective Extrusion of Ph3PO from β,γ,β'-Trioxo Ylides to give Doacylalkynes
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Sixteen examples of the previously unknown trioxo ylides 7 have been prepared by acylation of stabilized phosphorus ylides 8 with α-oxo acid chlorides 9.Extrusion of Ph3PO from these is readily achieved using FVP at 500 deg C in most cases, to afford the diacylalkynes 10 in moderate yield.Three examples failed to give the expected alkynes and the nature of the processes involved in these cases is certain.Fully assigned 13C NMR spectra are presented for the ylides and an unexpected pattern is observed in the value of JP-C for the three carbonyl carbons depending on the nature of the substituents present.There is some correlation between the value of 2JP-C for the central carbonyl carbon and the success of the pyrolysis although this is not complete.The method has been used to prepare a specifically 13C labelled acetylenic diester 14.
- Aitken, R. Alan,Herion, Hugues,Janosi, Amaya,Karodia, Nazira,Raut, Swati V.,et al.
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p. 2467 - 2472
(2007/10/02)
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- Pyrolysis of β,γ,β'-trioxo phosphorus ylides: Convenient synthesis of symmetrical and unsymmetrical diacylalkynes
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Flash vacuum pyrolysis of a series of 1,2,4-trioxo-3-triphenylphosphoranylidene-butane derivatives, formed by acylation of β-oxo-phosphorus ylides with α-oxo-acid chlorides, results in extrusion of Ph3PO exclusively across the 2,3-position to give diacylalkynes.
- Aitken,Herion,Janosi,Raut,Seth,Shannon,Smith
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p. 5621 - 5622
(2007/10/02)
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- (Alkyne)(2,2′-bipyridine)copper(I) complexes. Controlled formation of [Cu(bpy)(alkyne)]+ and {[Cu(bpy)]2(alkyne)}2+
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The addition of 1 equiv of 2,2′-bipyridine (bpy) to a solution of Cu(NCMe)4X (X = PF6--, SbF6-) followed by addition of an excess of alkyne (alkyne = 3-hexyne, 1-pentyne, methyl 2-butynoate, diphenylacetylene, diethyl acetylenedicarboxylate, phenylacetylene) leads to the preparation of [Cu(bpy)(alkyne)]X complexes in good yield. In order to isolate pure products, the alkyne complexes must be precipitated in the presence of excess alkyne. The alkyne ligands are labile in solution, exchanging rapidly on the NMR time scale. Competition studies show that the relative affinities of the alkynes (and ethylene) for copper in this system are C2H4 ～ HC≡CPr > EtC≡CEt ～ DEAD > HC≡CPh > MeC≡CCO2Me > PhC≡CPh. Repeated precipitation from solutions that initially contain [Cu(bpy)(alkyne)]X (alkyne = diethyl acetylenedicarboxylate, phenylacetylene) complexes in the absence of added alkyne leads to the isolation of {[Cu-(bpy)]2(alkyne)}X2, complexes with a 2:1 copper:alkyne stoichiometry.
- Reger, Daniel L.,Huff, Mark F.
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