- Continuous photochemical benzylic bromination using: In situ generated Br2: Process intensification towards optimal PMI and throughput
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The detailed development of photochemical benzylic brominations using a NaBrO3/HBr bromine generator in continuous flow mode is reported. Optimization of the bromine generator enables highly efficient mass utilization by HBr recycling, coupled with fast interphase transfer within a microstructured photochemical reactor (405 nm LEDs). Intensification of the reaction system, including complete removal of organic solvent, allowed a reduction in PMI from 13.25 to just 4.33. The photochemical transformation achieved exceptionally high throughput, providing complete conversion in residence times as low as 15 s. The organic solvent-free preparation of two pharmaceutically relevant building blocks was demonstrated with outstanding mass efficiency, by monobromination (1.17 kg scale in 230 min, PMI = 3.08) or dibromination (15 g scale in 20 min, PMI = 3.64).
- Steiner, Alexander,Williams, Jason D.,De Frutos, Oscar,Rincón, Juan A.,Mateos, Carlos,Kappe, C. Oliver
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- AN IMPROVED PROCESS FOR PREPARATION OF VILANTEROL OR A PHARMACEUTICALLY ACCEPTABLE SALT THEREOF
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The invention discloses an improved process for preparation of Vilanterol or a pharmaceutically acceptable salt thereof with good yields and high purity.
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Page/Page column 7-8; 13
(2021/02/26)
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- Photocatalytic continuous bromination method
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The invention provides a photocatalytic continuous bromination method. The method comprises the following steps: carrying out a first-stage photocatalytic continuous bromination reaction on a materialcontaining an aromatic substrate with a structural general formula I and a bromination reagent in a first continuous illumination reactor to form a first continuous system; overflowing the obtained first continuous system into a second continuous illumination reactor for a second-stage photocatalytic continuous bromination reaction to form a second continuous system; and purifying the second continuous system, wherein the structural general formula I is shown in the specification, R is selected from any one of carboxyl, ester group, NO2, CN, C1 to C8 alkyl and alkoxy, and R1 is C1 to C8 alkyl; n is 1 or 2; X is N or C, and the bromination reagent is Nbromo succinimide or dibromohydantoin. According to the bromination reagent, the selectivity of a product is improved, so the yield of the product is improved; the photocatalytic continuous bromination reaction of the two stages effectively relieves the reaction heat accumulation, and enhances the yield of the target product.
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Paragraph 0041-0059; 0072
(2021/04/03)
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- tBuOK-Promoted Cyclization of Imines with Aryl Halides
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A transition-metal-free indole synthesis using radical coupling of 2-halotoluenes and imines via the later-stage C-N bond construction was reported for the first time. It includes an aminyl radical generation by C-H cleaving addition of 2-halotoluenes to imines via the carbanion radical relay and an intramolecular coupling of aryl halides with aminyl radicals. One standard condition can be used for all halides including F, Cl, Br, and I. No extra oxidant or transition metal is required.
- Li, Ya-Wei,Zheng, Hong-Xing,Yang, Bo,Shan, Xiang-Huan,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 4553 - 4556
(2020/06/08)
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- Silver-Catalyzed Decarboxylative Bromination of Aliphatic Carboxylic Acids
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The silver-catalyzed Hunsdiecker bromination of aliphatic carboxylic acids is described. With Ag(Phen)2OTf as the catalyst and dibromoisocyanuric acid as the brominating agent, various aliphatic carboxylic acids underwent decarboxylative bromination to provide the corresponding alkyl bromides under mild conditions. This method not only is efficient and general but also enjoys wide functional group compatibility. An oxidative radical mechanism involving Ag(II) intermediates is proposed.
- Tan, Xinqiang,Song, Tao,Wang, Zhentao,Chen, He,Cui, Lei,Li, Chaozhong
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supporting information
p. 1634 - 1637
(2017/04/11)
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- Rasta resin-triphenylphosphine oxides and their use as recyclable heterogeneous reagent precursors in halogenation reactions
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Heterogeneous polymer-supported triphenylphosphine oxides based on the rasta resin architecture have been synthesized, and applied as reagent precursors in a wide range of halogenation reactions. The rasta resin-triphenylphosphine oxides were reacted with either oxalyl chloride or oxalyl bromide to form the corresponding halophosphonium salts, and these in turn were reacted with alcohols, aldehydes, aziridines and epoxides to form halogenated products in high yields after simple purification. The polymersupported triphenylphosphine oxides formed as a byproduct during these reactions could be recovered and reused numerous times with no appreciable decrease in reactivity.
- Xia, Xuanshu,Toy, Patrick H.
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supporting information
p. 1397 - 1405
(2014/07/22)
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- 4-Phenylpyrrolo[3,4-c]carbazole-1,3(2H,6H)-dione inhibitors of the checkpoint kinase Wee1. structure-activity relationships for chromophore modification and phenyl ring substitution
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High-throughput screening has identified a novel class of inhibitors of the checkpoint kinase Wee1, which have potential for use in cancer chemotherapy. These inhibitors are based on a 4-phenylpyrrolo[3,4-c]-carbazole-1,3(2H,6H)- dione template and have been shown by X-ray crystallography to bind at the ATP site of the enzyme. An extensive study of the effects of substitution around this template has been carried out, which has identified substituents which lead to improvements in potency and selectivity for Wee1. While retention of the maleimide ring and pendant 4-phenyl group is necessary for potency, replacement of the carbazole nitrogen by oxygen is well tolerated and results in improved Wee1 selectivity against the related checkpoint kinase Chk1. Wee1 potency and selectivity are also enhanced by the incorporation of lipophilic functionality at the 2′-position of the 4-phenyl ring, and Wee1 selectivity against Chk1 is favored by C3-C5 alkyl substitution of the carbazole nitrogen. These studies provide a basis for the design of active analogues of the pyrrolocarbazole lead with improved physical properties.
- Palmer, Brian D.,Thompson, Andrew M.,Booth, R. John,Dobrusin, Ellen M.,Kraker, Alan J.,Lee, Ho H.,Lunney, Elizabeth A.,Mitchell, Lorna H.,Ortwine, Daniel F.,Smaill, Jeff B.,Swan, Leesa M.,Denny, William A.
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p. 4896 - 4911
(2007/10/03)
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- 6-HYDROXY-2-NAPHTHYLCARBINOL AND PROCESS FOR THE PREPARATION THEREOF
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6-Hydroxy-2-naphthylcarbinol useful as a synthetic intermediate for preparation of 6-hydroxy-2-naphthaldehyde represented by the following formula (I), and a method for preparing 6-hydroxy-2-naphthylcarbinol comprising the step of reducing 6-hydroxy-2-naphthalenecarboxylic acid.
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- Ultra-short acting neuromuscular blocking agents; di- and tri-substituted benzyl bisquaternary ammonium derivatives of bis(tropan-3α-ol)-diesters
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Based on previous experiences with bisquaternary ammonium derivatives of bistropine esters of dicarboxylic acids we designed, synthesized and pharmacologically evaluated seventy dicarboxylic acid esters of tropine (tropan-3α-ol) bearing substituted N-benzyl quaternizing groups. Many of the quaternary derivatives of these bistropine diesters showed high neuromuscular blocking potency, very short onset and ultrashort or short duration of action in experimental animals.
- Gyermek, Laszlo,Lee, Chingmuh,Cho, Young-Moon,Nguyen, Nguyen,Tsai, Shen-Kou
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p. 116 - 136
(2007/10/03)
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- Cobalt-mediated Reactions in Synthesis. The Degradation of Carboxylic Acids to Functionalised Noralkanes via Acylcobalt Salophen Intermediates
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Arylmethyl- and allyl-carbonylcobalt salophen complexes, e.g. (7), (8), (9), and (22), readily undergo carbon-to-cobalt-bond homolysis and in situ decarbonylation, producing new alkyl radical centres which can be intercepted with oxygen-, nitrogen-, halogen-, sulphur-, and selenium-containing trapping agents leading to functionalised noralkanes.The sequence constitutes a useful, and in some cases more flexible, variant of the classical Hunsdiecker reaction, and amounts to a cobalt equivalent of the Barton radical decarboxylation reaction of carboxylic acids via their corresponding thiohydroxamic esters.In a similar manner, irradiation of the oxy-substituted acylcobalt salen reagents (25) and (26) in the presence of tetramethylpiperidine oxide produces the products (14) and (27), respectively, resulting from homolysis-decarboxylation and alkyl-radical trapping.In the absence of radical-trapping agents, irradiation of (7c) produces (18), and irradiation of (29) leads to the but-2-enolide (32).
- Patel, Vinod F.,Pattenden, Gerald,Thompson, David M.
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p. 2729 - 2734
(2007/10/02)
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- FREE RADICAL REACTIONS INITIATED BY ORGANOCOBALT COMPLEXES. A NEW METHOD FOR THE DEGRADATION OF CARBOXYLIC ACIDS TO FUNCTIONALISED NOR-ALKANES VIA ACYLCOBALT SALOPHEN INTERMEDIATES.
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Arylmethyl- and allyl-acylcobalt salophens, undergo facile C-Co bond homolysis and in situ decarbonylation, producing new (alkyl) radical centres which can be intercepted with oxygen, nitrogen, halogen, sulphur and selenium containing radical trapping agents, leading to functionalised nor-alkanes (Scheme).
- Patel, Vinod F.,Pattenden, Gerald
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p. 707 - 710
(2007/10/02)
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- Solvolysis of 2-substituted-9-(ortho-substituted) phenylmethyl)fluoren-9-yltrimethylammonium ions in various solvents
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The solvolytic reaction of several 9-(ortho-substituted phenylmethyl)fluoren-9-yltrimethylammonium salts has been investigated in several different solvents.Substitution and elimination products were found for the reactions in all solvents studied, with the exceptions that rection in both tert-butyl alcohol and chloroform led exclusively to the alkene product.The observed rate constants for alkene formation and the percent alkene were measured and it was found that the di-ortho compounds reacted at a faster rate but produced less alkene than the reaction of the corresponding mono-ortho salts.Hydrogen-deuterium isotope effects were also determined for the various reactions.The results are discussed in terms of the reaction proceeding by way of the E1 mechanism, where steric acceleration promotes the loss of the bulky ammonium leaving group to give the carbocation intermediate.
- Smith, Peter James,Pradhan, Jyotsna
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p. 1060 - 1071
(2007/10/02)
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