- Oxidation of aromatic compounds: XI. Oxidation of methyl 3-(4-methoxyphenyl)propynoate in the system CF3COOH-CH 2Cl2-PbO2
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Oxidation of methyl 3-(4-methoxyphenyl)propynoate in the system CF 3COOH-CH2Cl2-PbO2 at 0-2°C within 2 h affords in a preparative yield of 55% a product of oxidative dimerization, dimethyl 2,3-bis(4-methoxyphenylcarbonyl)but-2-ene-1,4- dicarboxylate (II) whose double bond is in E-configuration according to X-ray diffraction data.
- Vasilyev,Fundamenskii,Savchenkov,Rudenko
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Read Online
- Z-Selective phosphine promoted 1,4-reduction of ynoates and propynoic amides in the presence of water
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Phosphine-mediated reductions of substituted propynoic esters and amides in the presence of water yield the partially reduced α,β-unsaturated esters and amides with highZ-selectivity. The competitivein situ ZtoE-isomerization of the product in some cases lowers theZtoEratios of the isolated α,β-unsaturated carbonyl products. Reaction time and the amounts of phosphine and water in the reaction mixture are the key experimental factors which control the selectivity by preventing or reducing the rates ofZ- toE-product isomerization. Close reaction monitoring enables isolation of theZ-alkenes with high selectivities. The computational results suggest that the reactions could be highlyZ-selective owing to the stereoselective formation of theE-P-hydroxyphosphorane intermediate.
- Drikermann, Denis,Kupfer, Stephan,Seifert, Fabian,Steinmetzer, Johannes,Vilotijevic, Ivan,Zi, You
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supporting information
p. 6092 - 6097
(2021/07/21)
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- Au(I) Catalyzed Synthesis of Densely Substituted Pyrazolines and Dihydropyridines via Sequential Aza-Enyne Metathesis/6π-Electrocyclization
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A gold(I) autotandem catalysis protocol is reported for the de novo synthesis of densely substituted pyrazolines and dihydropyridines from the corresponding imine derivatives in a highly regioselective fashion via a one-pot aza-enyne metathesis/6π-electrocyclization sequence. The substituents on the nitrogen atom of the imine perfectly control the reaction pathways from the pivotal 1-azabutadiene intermediate; thus, carbazates were converted into pyrazolines via 6π-electrocyclization of α,β-unsaturated hydrazones, while aryl imines provided dihydropyridines via 6π-electrocyclization of 3-azahexatrienes.
- Sugimoto, Kenji,Kosuge, Shuto,Sugita, Takae,Miura, Yuka,Tsuge, Kiyoshi,Matsuya, Yuji
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supporting information
p. 3981 - 3985
(2021/05/26)
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- trans-Selective hydrocyanation of ynoates, ynones and ynoic acids catalyzed by nucleophilic phosphines
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trans-Selective hydrocyanation of ynoates and ynones in the presence of TMSCN and an alcohol additive are catalyzed by nucleophilic phosphines. The trisubstituted E-olefin products of anti-addition of hydrogen cyanide to the alkyne are produced with high regio- and stereoselectivity. The alcohol additive reacts with TMSCN to produce hydrogen cyanide in situ. Ynoic acids undergo the phosphine catalyzed hydrocyanation in the presence of TMSCN under aprotic conditions only. In these reactions, TMSCN reacts with the acid to generate hydrogen cyanide and the silyl ester which, unlike the acid, undergoes phosphine catalyzed hydrocyanation and gives the stereo-defined E-2-cyano-acrylic acids after work up.
- Meyer, Maximilian,Peri?, Milica,Sch?mberg, Fritz,Vilotijevi?, Ivan
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supporting information
(2021/10/04)
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- Organocatalytic trans Phosphinoboration of Internal Alkynes
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We report the first trans phosphinoboration of internal alkynes. With an organophosphine catalyst, alkynoate esters and the phosphinoboronate Ph2P-Bpin are efficiently converted into the corresponding trans-α-phosphino-β-boryl acrylate products in moderate to good yield with high regio- and Z-selectivity. This reaction operates under mild conditions and demonstrates good atom economy, requiring only a modest excess of the phosphinoboronate. X-ray crystallography experiments allowed structural assignment of the unprecedented and densely functionalized (Z)-α-phosphino-β-boryl acrylate products.
- Fritzemeier, Russell G.,Nekvinda, Jan,Rosenblum, Carol Ann,Santos, Webster L.,Slebodnick, Carla,Vogels, Christopher M.,Westcott, Stephen A.
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supporting information
p. 14358 - 14362
(2020/07/04)
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- Oxidant- and additive-free simple synthesis of 1,1,2-triiodostyrenes by one-pot decaroboxylative iodination of propiolic acids
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A metal- and oxidant-free facile synthesis of a range of 1,1,2-triiodostryrene derivatives has been developed which utilizes a simple decarboxylative triiodination of propiolic acids using molecular iodine and sodium acetate in a one-pot manner. Electron-
- Ghosh, Subhankar,Ghosh, Rajat,Chattopadhyay, Shital K.
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supporting information
(2020/09/15)
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- Cobalt(III)-Catalyzed Intermolecular Carboamination of Propiolates and Bicyclic Alkenes via Non-Annulative Redox-Neutral Coupling
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A cobalt(III)-catalyzed, redox-neutral, intermolecular carboamination of propiolates and bicyclic alkenes was developed. This non-annulative coupling strategy features atom economy, high regioselectivity, good yields, and functional groups tolerance. Such a carboamination reaction was applied to modified phenols from the corresponding phenols under mild conditions.
- Zhu, Yuelu,Chen, Feng,Zhao, Xinyang,Yan, Dingyuan,Yong, Wanxiong,Zhao, Jing
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supporting information
p. 5884 - 5888
(2019/08/20)
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- Synthesis of 1-Amino-2 H-quinolizin-2-one Scaffolds by Tandem Silver Catalysis
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An efficient tandem cycloisomerization-amination reaction catalyzed by silver is described. This rapid and atom-economic reaction delivered 1-amino-2H-quinolizin-2-one scaffolds in high yields under mild conditions. The reaction could be extended to an asymmetric version albeit with moderate enantioselective excess of the products. In addition, the products can be easily reduced into various azabicycles containing 4-pyridones, which are important building blocks in organic synthesis.
- Min, Xiao-Long,Sun, Chao,He, Ying
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supporting information
p. 724 - 728
(2019/02/21)
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- Trans-Hydroboration of Propiolamides: Access to Primary and Secondary (E)-β-Borylacrylamides
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A base-mediated trans-hydroboration of propiolamides that provides access to previously elusive primary and secondary (E)-β-borylacrylamide products has been developed. In the presence of n-butyllithium and pinacolborane, complete regioselectivity and ste
- Grams, R. Justin,Fritzemeier, Russell G.,Slebodnick, Carla,Santos, Webster L.
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supporting information
p. 6795 - 6799
(2019/08/26)
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- Trans -Hydroboration vs. 1,2-reduction: Divergent reactivity of ynones and ynoates in Lewis-base-catalyzed reactions with pinacolborane
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Ynones and ynoates react with pinacolborane in a divergent manner in the presence of nucleophilic phosphine catalysts. Ynones are transformed to the corresponding propargyl alcohols in good yields with high regio- and chemoselectivity. Ynoates undergo highly regio- and stereoselective trans-hydroboration to produce E-vinylboronates. Impressive divergence in reactivity of ynones and ynoates can be traced back to the mechanistic aspects of 1,2-reduction and trans-hydroboration. A comparative analysis of the two pathways paints a complex picture in which different reaction rates control selectivity in these seemingly unrelated processes and explains how sufficiently acidic protons in the reaction mixtures can be used to steer the selectivity in different directions.
- Zi, You,Sch?mberg, Fritz,Seifert, Fabian,G?rls, Helmar,Vilotijevic, Ivan
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supporting information
p. 6341 - 6349
(2018/09/10)
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- Salt-Free Strategy for the Insertion of CO2 into C?H Bonds: Catalytic Hydroxymethylation of Alkynes
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A copper(I) catalyst enables the insertion of carbon dioxide into alkyne C?H bonds by using a suitable organic base with which hydrogenation of the resulting carboxylate salt with regeneration of the base becomes thermodynamically feasible. In the presence of catalytic copper(I) chloride/4,7-diphenyl-1,10-phenanthroline, polymer-bound triphenylphosphine, and 2,2,6,6-tetramethylpiperidine as the base, terminal alkynes undergo carboxylation at 15 bar CO2 and room temperature. After filtration, the ammonium alkynecarboxylate can be hydrogenated to the primary alcohol and water at a rhodium/molybdenum catalyst, regenerating the amine base. This demonstrates the feasibility of a salt-free overall process, in which carbon dioxide serves as a C1 building block in a C?H functionalization.
- Wendling, Timo,Risto, Eugen,Krause, Thilo,Goo?en, Lukas J.
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supporting information
p. 6019 - 6024
(2018/03/27)
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- Palladium-Catalyzed Hydroalkylation of Alkynes with Cyclopropanols: Access to γ,δ-Unsaturated Ketones
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A palladium-catalyzed hydroalkylation of alkynes with cyclopropanols has been developed. This reaction provided a straightforward way to the synthesis of γ,δ-unsaturated ketones in moderate to good yields, exhibiting high atom economy and Z/E selectivity. Deuterated tri-substituted alkenes could also be expediently produced by using deuterium oxide as a co-solvent. (Figure presented.).
- Liu, Hao,Fu, Zhiyuan,Gao, Shang,Huang, Yue,Lin, Aijun,Yao, Hequan
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supporting information
p. 3171 - 3175
(2018/08/01)
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- Cobalt(III)-Catalyzed Construction of Benzofurans, Benzofuranones and One-Pot Orthogonal C?H Functionalizations to Access Polysubstituted Benzofurans
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Benzofuran and benzofuranone derivatives have been synthesized through exclusive 5-exo-dig intramolecular hydroarylation using the amide-directed, cost-effective, high-valent Cp*CoIII-catalytic system. Challenging one-pot, orthogonal C?H functionalizations using two different electrophiles are also reported to afford polysubstituted benzofurans. Several valuable functional group interconversions along with removal of the amide directing group provide a route to access several diversely functionalized benzofurans. The mechanistic study suggests a reversible cobaltation step is operative here. (Figure presented.).
- Bera, Sourav Sekhar,Debbarma, Suvankar,Jana, Sripati,Maji, Modhu Sudan
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supporting information
p. 2204 - 2210
(2018/06/07)
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- Transition Metal-Free Trans Hydroboration of Alkynoic Acid Derivatives: Experimental and Theoretical Studies
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We report a phosphine-catalyzed trans hydroboration of alkynoate esters and amides. The reaction proceeds under mild conditions with exclusive (E)-selectivity to afford (E)-β-boryl acrylates and (E)-β-boryl acrylamides in good to excellent yields. The reaction is tolerant of a variety of functional groups and allows efficient access to novel oxaboroles as well as a pargyline derivative (MAO inhibitor). Theoretical calculations suggest an internal hydride generates a phosphonium allenoxyborane followed by the formation of a key phosphonocyclobutene intermediate that collapses in a stereoselective, rate-limiting step.
- Fritzemeier, Russell,Gates, Ashley,Guo, Xueying,Lin, Zhenyang,Santos, Webster L.
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p. 10436 - 10444
(2018/07/21)
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- Enantioselective Palladium-Catalyzed Oxidative Cascade Cyclization of Aliphatic Alkenyl Amides
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The catalyst system of Pd(TFA)2/(S,S)-diPh-pyrox is reported to promote the highly efficient enantioselective oxidative cascade cyclization of alkene-tethered aliphatic acrylamides under mild aerobic conditions. A series of pyrrolizidine derivatives have been synthesized in good yield and excellent enantioselectivity. Deuterium-labeling experiments have revealed that the reaction proceeded through an anti-aminopalladation (anti-AP) pathway with high selectivity. The transition states for the anti-AP step have been calculated to account for the observed enantioselectivity.
- Du, Wei,Gu, Qiangshuai,Li, Yang,Lin, Zhenyang,Yang, Dan
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p. 316 - 319
(2017/04/21)
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- One-pot synthesis of propynoates and propynenitriles
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An efficient transformation towards propynoates and propynenitriles is herein described. The practical methodology was conducted at low temperature (-78 or -60 °C) in a one-pot manner with the assistance of base rather than any transition metal catalysts. The base-induced protocol exhibits good functional group tolerance (up to 28 examples) and high efficiency (up to 92% yields) towards substituted acetylenes of great synthetic significance, which was also well demonstrated by the gram-scale reactions.
- Shu, Fan,Zheng, Qingjuan,Dong, Wanrong,Peng, Zhihong,An, Delie
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p. 144 - 148
(2017/02/10)
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- Palladium-Catalyzed Synthesis of Conjugated Allenynes via Decarboxylative Coupling
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A new strategy to access conjugated allenynes via a decarboxylative coupling of propargyl esters of propiolates has been developed. In this process, allenyl-palladium intermediates are coupled with acetylides that are generated in situ to form the conjuga
- Smith, Mary K.,Tunge, Jon A.
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supporting information
p. 5497 - 5500
(2017/10/25)
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- Oxidative Alkoxycarbonylation of Alkynes by Means of Aryl α-Diimine Palladium(II) Complexes as Catalysts
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The straightforward in situ synthesized bis(2,6-diisopropyl)acenaphthenequinonediimine palladium triflate catalyst was generally employed for both the mono-alkoxycarbonylation of terminal alkynes, and the bis-alkoxycarbonylation of 1,2-disubstituted alkynes by using mild reaction conditions [carbon monoxide pressure (PCO)=4 bar, temperature=20 °C]. Utilizing low catalyst loading (down to 0.5 mol%), a variety of propiolic esters were synthesized with good to excellent isolated yields. Most importantly the system was very efficient not only with methanol but also with a range of different alcohols, starting from the less hindered benzyl alcohol to the most hindered ones, such as isopropyl alcohol and tert-butyl alcohol. In addition, aromatic and aliphatic 1,2-disubstituted alkynes were converted into maleic acid derivatives, together with an acid-catalyzed isomerization reaction, showing modest to good selectivity and excellent combined yields. In particular 3-hexyne showed a satisfactory degree of selectivity for the maleic diesters of methanol and benzyl alcohol, obtaining the corresponding products with good isolated yields. (Figure presented.).
- Beltrani, Michela,Carfagna, Carla,Milani, Barbara,Mancuso, Raffaella,Gabriele, Bartolo,Fini, Francesco
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p. 3244 - 3253
(2016/10/21)
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- SF5-Enolates in Ti(IV)-Mediated Aldol Reactions
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The F···Ti bonding in the transition structures determines high trans- and syn-diastereoselectivities for aldol reactions of SF5-acetates with aldehydes in the presence of TiCl4 in the non-nucleophilic solvent CH2Cl2
- Ponomarenko, Maksym V.,Grabowsky, Simon,Pal, Rumpa,R?schenthaler, Gerd-Volker,Fokin, Andrey A.
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p. 6783 - 6791
(2016/08/16)
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- Copper-Catalyzed Domino Synthesis of Benzo[4,5]imidazo[1,2-a]pyrimidin-4(10H)-ones using Cyanamide as a Building Block
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An efficient and practical copper-catalyzed domino synthesis of benzo[4,5]imidazo[1,2-a]pyrimidin-4(10H)-ones has been developed. The protocol uses N-(2-halophenyl)-3-alkylpropiolamides and cyanamide as the starting materials, inexpensive copper(I) iodide and pipecolinic acid as the catalyst and ligand, and the corresponding products were obtained in moderate to good yields.
- Lou, Zhenbang,Wu, Xudong,Yang, Haijun,Zhu, Changjin,Fu, Hua
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supporting information
p. 3961 - 3968
(2016/01/25)
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- Synthesis of fluorenone and anthraquinone derivatives from aryl- and aroyl-substituted propiolates
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Fluorenone derivatives were generated from aryl-substituted propiolates via a cobalt-catalyzed Diels-Alder reaction/DDQ-oxidation and Friedel-Crafts-type cyclization. Several functional groups are tolerated, and good to excellent overall yields (up to 89%) could be achieved. For the synthesis of anthraquinone derivatives, aroyl-substituted propiolates were applied in a zinc iodide catalyzed Diels-Alder reaction with 1,3-dienes. The subsequent DDQ oxidation and Friedel-Crafts-type cyclization led to symmetrical as well as some unsymmetrical anthraquinones in good to excellent yields of up to 87% over the three-step reaction sequence.
- Puenner, Florian,Schieven, Justin,Hilt, Gerhard
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supporting information
p. 4888 - 4891
(2013/10/08)
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- Construction of 2-substituted-3-functionalized benzofurans via intramolecular heck coupling: Application to enantioselective total synthesis of daphnodorin B
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A novel approach was developed for the synthesis of 2-substituted-3- functionalized benzofurans, using an intramolecular Heck reaction which was further applied in the first enantioselective total synthesis of Daphnodorin B.
- Yuan, Hu,Bi, Kai-Jian,Li, Bo,Yue, Rong-Cai,Ye, Ji,Shen, Yun-Heng,Shan, Lei,Jin, Hui-Zi,Sun, Qing-Yan,Zhang, Wei-Dong
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p. 4742 - 4745
(2013/10/08)
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- Cationic rhodium(I)-catalyzed regioselective tandem heterocyclization/[3+2] cycloaddition of 2-(1-alkynyl)-2-alken-1-ones with alkynes
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RhI in two minds: A RhI-catalyzed tandem heterocyclization/[3+2] cycloaddition reaction was developed that provides rapid, efficient, and stereoselective access to highly substituted cyclopenta[c]furans from readily available 2-(1-alkynyl)-2-alken-1-ones and alkynes (see scheme). The cationic RhI acts as both a Lewis acid and a conventional transition-metal catalyst, providing the first example of a RhI species acting as a Lewis acid. Copyright
- Gao, Hongyin,Zhang, Junliang
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supporting information; experimental part
p. 2777 - 2782
(2012/04/04)
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- Acid-catalyzed synthesis of bicyclo[3. n.1]alkenediones
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An acid-catalyzed Dieckmann-type reaction has been developed to access functionalized bicyclo[3.2.1]alkenediones. This methodology has been successfully extended to more substituted and larger ring homologues, providing a new and efficient route to the core of numerous attractive natural products and their analogues.
- Michaelides, Iacovos N.,Darses, Benjamin,Dixon, Darren J.
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p. 664 - 667
(2011/04/24)
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- Synthesis and biological activities of new furo[3,4-b]carbazoles: Potential topoisomerase II inhibitors
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New 1,5-Dihydro-4-(substituted phenyl)-3H-furo[3,4-b]carbazol-3-ones were synthesised via a key step Diels-Alder reaction under microwave irradiation. 3-Formylindole was successfully used in a 6-step synthesis to obtain those complex heterocycles. The Diels-Alder reaction generating the carbazole ring was optimised under thermal conditions or microwave irradiation. After cleavage of functional groups, DNA binding, topoisomerase inhibition and cytotoxic properties of the new-formed furocarbazoles were investigated. These carbazoles do not present a strong interaction with the DNA, and do not modify the relaxation of the DNA in the presence of topoisomerase I or II except for one promising compound. This compound is a potent topoisomerase II inhibitor, and its cellular activity is not moderated compared to etoposide. The synthesis of these molecules allowed the generalisation of the method using indole and 5-OBn indole and several benzaldehydes. The synthesis of these molecules produced chemical structures endowed with promising cytotoxic and topoisomerase II inhibition activities.
- Hajbi, Youssef,Neagoie, Cléopatra,Biannic, Bérenger,Chilloux, Aurélie,Vedrenne, Emeline,Baldeyrou, Brigitte,Bailly, Christian,Mérour, Jean-Yves,Rosca, Sorin,Routier, Sylvain,Lansiaux, Amélie
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experimental part
p. 5428 - 5437
(2010/12/25)
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- Copper-catalyzed cross-coupling of alkyl and aryl grignard reagents with alkynyl halides
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(Chemical Equation Presented) Good old copperl A new general procedure to couple aliphatic and aromatic Grignard reagents with alkynyl halides under copper catalysis is described (see scheme; NMP=N-methylpyrrolidinone). The reaction is chemoselective and allows preparation of a vast array of simple and functionalized internal alkynes in high yields.
- Cahiez, Gerard,Gager, Olivier,Buendia, Julien
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supporting information; experimental part
p. 1278 - 1281
(2010/05/18)
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- Synthesis and rearrangement of dewar benzenes into biaryls: Experimental evidence for conrotatory ring opening
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Rearrangement of aryl-substituted Dewar benzenes into the corresponding biaryls may serve as an alternative pathway for synthesis of sterically hindered biaryls. The kinetic data obtained from thermal rearrangements of Dewar benzenes provide experimental
- Jankova, Stepanka,Dracinsky, Martin,Cisarova, Ivana,Kotora, Martin
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- Pyranone, thiopyranone, and pyridone inhibitors of phosphatidylinositol 3-kinase related kinases. Structure-activity relationships for DNA-dependent protein kinase inhibition, and identification of the first potent and selective inhibitor of the ataxia telangiectasia mutated kinase
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Structure-activity relationships have been investigated for inhibition of DNA-dependent protein kinase (DNA-PK) and ATM kinase by a series of pyran-2-ones, pyran-4-ones, thiopyran-4-ones, and pyridin-4-ones. A wide range of IC50 values were observed for pyranones and thiopyranones substituted at the 6-position, with the 3- and 5-positions proving intolerant to substitution. Related pyran-2-ones, pyran-4-ones, and thiopyran-4-ones showed similar IC50 values against DNA-PK, whereas the pyridin-4-one system proved, in general, ineffective at inhibiting DNA-PK. Extended libraries exploring the 6-position of 2-morpholinopyran-4-ones and 2-morpholino- thiopyrano-4-ones identified the first highly potent and selective ATM inhibitor 2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one (151C; ATM; IC50 = 13 nM) and revealed constrained SARs for ATM inhibition compared with DNA-PK. One of the most potent DNA-PK inhibitors identified, 2-(4-methoxyphenyl)-6- (morpholin-4-yl)pyran-4-one (16; DNA-PK; IC50 = 220 nM) effectively sensitized HeLa cells to the topoisomerase II inhibitor etoposide in vitro.
- Hollick, Jonathan J.,Rigoreau, Laurent J. M.,Cano-Soumillac, Celine,Cockcroft, Xiaoling,Curtin, Nicola J.,Frigerio, Mark,Golding, Bernard T.,Guiard, Sophie,Hardcastle, Ian R.,Hickson, Ian,Hummersone, Marc G.,Menear, Keith A.,Martin, Niall M. B.,Matthews, Ian,Newell, David R.,Ord, Rachel,Richardson, Caroline J.,Smith, Graeme C. M.,Griffin, Roger J.
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p. 1958 - 1972
(2008/02/02)
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- The concise synthesis of chalcone, indanone and indenone analogues of combretastatin A4
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A series of aryl- and aroyl-substituted chalcone analogues of the tubulin binding agent combretastatin A4 (1) were prepared, using a recently introduced one-pot palladium-mediated hydrostannylation-coupling reaction sequence. These chalcones were converte
- Kerr, Daniel J.,Hamel, Ernest,Jung, M. Katherine,Flynn, Bernard L.
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p. 3290 - 3298
(2008/02/07)
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- Preparation of 1-aryl-2-bromo-3,3-difluorocyclopropenes
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1-Aryl-2-bromo-3,3-difluorocyclopropanes were prepared from the reaction of 2′,2′-difluorostyrene and dibromocarbene instead of from 1-aryl-2-haloacetylenes and difluorocarbene. These results are rationalised by the energy gap between HOMO(styrene), HOMO(acetylene) and LUMO(CX2). The title compounds were converted to methyl arylpropynoate in MeOH solution in quantitative yield.
- Lin, Shaw-Tao,Chen, Li-Chwen,Lee, Chun-Jen
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p. 353 - 355
(2007/10/03)
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- Oxidation of aromatic compounds: XII. Regio- and stereoselective oxidative dimerization of alkyl 3-arylpropynoates in the system CF3CO 2H-CH2Cl2-PbO2
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Regio- and stereoselective oxidative dimerization of alkyl 3-arylpropynoates in the system CF3CO2H-CH 2Cl2-PbO2 (1-30 h, 0-20°C) leads to dialkyl (E)-2,3-bis(arylcarbonyl)-2-butene-1,4-dioates with trans arrangement of the substituents at the double bond.
- Savechenkov,Vasil'ev,Rudenko
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p. 1279 - 1283
(2007/10/03)
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- 2,6-Disubstituted pyran-4-one and thiopyran-4-one inhibitors of DNA-dependent protein kinase (DNA-PK)
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6-Aryl-2-morpholin-4-yl-4H-pyran-4-ones and 6-aryl-2-morpholin-4-yl-4H-thiopyran-4-ones were synthesised and evaluated as potential inhibitors of the DNA repair enzyme DNA-dependent protein kinase (DNA-PK). Several compounds in each series exhibited super
- Hollick, Jonathan J.,Golding, Bernard T.,Hardcastle, Ian R.,Martin, Niall,Richardson, Caroline,Rigoreau, Laurent J. M.,Smith, Graeme C. M.,Griffin, Roger J.
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p. 3083 - 3086
(2007/10/03)
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- Highly satisfactory procedures for the Pd-catalyzed cross coupling of aryl electrophiles with in situ generated alkynylzinc derivatives.
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[reaction: see text] Two new and very efficient procedures (Procedures A and B) are reported for the Pd-catalyzed cross coupling of aryl electrophiles with terminal alkynes via their in situ conversion into alkynylzinc derivatives. Procedure A is particul
- Anastasia,Negishi Ei
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p. 3111 - 3113
(2007/10/03)
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- A new method for synthesis of methyl arylpropiolates by direct heck coupling of aryl iodide and methyl propiolate in presence of K2CO3
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A protocol for the efficient direct cross coupling of esters of propiolic acid and of aryl iodides with a Pd(PPh3)2Cl2/copper(I) iodide catalyst system in the presence of K2CO3 has been developed.
- Eckert, Thomas,Ipaktschi, Junes
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p. 327 - 335
(2007/10/03)
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- Synthesis of 2-amino-6-phenyl-4H-pyran-4-ones
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The treatment of a series of phenylacetylenic β-keto amides with methanesulfonic acid produces a high yielding intramolecular cyclization to the corresponding 2-amino-6-phenyl-4H-pyran-4-ones.
- Morris,Wishka
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- Mild Palladium-catalysed Carbonylation of Alkynylphenyliodonium Toluene-p-sulphonates under Carbon Monoxide at Atmospheric Pressure
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Alkoxycarbonylation of alkynylphenyliodonium toluene-p-sulphonates catalysed by a palladium catalyst proceeded under carbon monoxide at atmospheric pressure at room temperature to give alkyne carboxylates in high yields.
- Kitamura, Tsugio,Mihara, Ichiro,Taniguchi, Hiroshi,Stang, Peter J.
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p. 614 - 615
(2007/10/02)
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- Hypervalent Iodine Oxidation of 5-Substituted and 4,5-Disubstituted Pyrazol-3(2H)-ones: A Facile Synthesis of Methyl-2-alkynoates and Methyl 2,3-alkadienoates
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Hypervalent iodine oxidation of various 5-substituted pyrazol-3(2H)-ones (1a-h) with iodobenzene diacetate or iodosobenzene in methanol results in fragmentative loss of molecular dinitrogen to yield methyl 2-alkynoates (2a-h).However, 5-methyl-4-substituted pyrazol-3(2H)-ones (3a-d) under similar conditions yield methyl 2,3-allenic esters (4a-d).Methyl 2,3-cycloalkadienoates (6a-e) are obtained by the oxidative cleavage of 4,5-polymethylene pyrazol-3(2H)-ones (5c-e) using iodobenzene diacetate or iodosobenzene in methanol. 5-Methyl-4,4-disubstituted pyrazol-3(2H)-ones (7a-b) were found not to undergo raction under similar conditions.The scope and mechanism of these reactions are discussed.
- Moriarty, R. M.,Vaid, R. K.,Ravikumar, V. T.,Hopkins, T. E.,Farid, P.
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p. 1605 - 1610
(2007/10/02)
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- Preparation of Arylpropiolate Esters from Trichlorocyclopropenium Cation and Elaboration of the Esters to Unsymmetrical 1,4-Pentadiyn-3-ones and Unsymmetrical Tellurapyranones
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The addition of aromatic compounds including thiophene, naphthalene derivatives, and some benzene derivatives to trichlorocyclopropenium cation gave nearly quantitative yields of 1-aryl-2,3,3-trichlorocyclopropenes.Alcoholysis of the cyclopropene derivatives gave either arylpropiolate esters or arylpropiolate orthoesters (in the presence of added amine base).The arylpropiolates can be converted to unsymmetrical 1,4-pentadiyn-3-ones by two different approaches.The first approach involved reduction of the arylpropiolate esters with diisobutylaluminum hydride to give the corresponding propargyl alcohol.Pyridinium chlorochromate or manganese dioxide oxidation of the alcohol gave the propargyl aldehydes.Addition of a lithium acetylenide gave a 1,4-pentadiyn-3-ol, which could then be oxidized to the 1,4-pentadiyn-3-one with 10percent chromic acid or manganese dioxide.The second pathway used a Lewis acid mediated coupling of a propargylic acid chloride with a (trimethylsilyl)acetylene to give the 1,4-pentadiyn-3-ones directly.The coupling of 2-thiophenepropiolic acid chloride gave the product of HCl addition to the expected 1,4-diynone.The regiochemistry of addition was determined to be chloride addition to the thiophene-bearing triple bond on the basis of 1H NMR studies.The diynones were converted to unsymmetrical 2,6-disubstituted tellura-4H-pyran-4-ones with disodium telluride anion.
- Wadsworth, Donald H.,Geer, Susan M.,Detty, Michael R.
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p. 3662 - 3668
(2007/10/02)
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