- Grob-Type Fragmentation Releases Paracyclophane Ring Strain in a Late-Stage Precursor of Haouamine A
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A ketene [2 + 2]-addition, an intramolecular aldol reaction, a Suzuki-Miyaura coupling, and a chemoselective lactam reduction were used to prepare a late-stage precursor of haouamine A. Exposure to acid led to a Grob-type fragmentation of the strained 3-aza[7]paracyclophane ring, followed by a tandem Pictet-Spengler reaction of the intermediate iminium ion and conversion to a novel 1,4a-propanocyclopenta[b]pyridine. This cascade reaction might also be relevant for the mechanism of action of the natural product.
- Cao, Liming,Wang, Chenbo,Wipf, Peter
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- Mild conversion of β-diketones and β-ketoesters to carboxylic acids
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A mild protocol for the conversion of β-ketoesters and β-diketones to carboxylic acids with use of CAN in CH3CN is described. The method is compatible with a number of functional groups, and can generate carboxylic acids under neutral conditions at room temperature. The reaction is fast and general, providing an alternative method to the commonly used malonic ester acid preparation. Initial mechanistic studies show that initial oxidation of the enol form of the β-dicarbonyl initiates the reaction. The presence of nitrate as an oxidant ligand or as an additive is critical for success of the reaction.
- Zhang, Yang,Jiao, Jingliang,Flowers II, Robert A.
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- Samarium diiodide reduction of cinnamic acids
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The method for measuring SmI2 reduction rates is expanded to a wider range of organic compounds by using not only GC or GC/MS, but also HPLC as the detecting tool. The reduced substrates are not only confined to water insoluble compounds or low boiling compounds only. Water soluble cinnamic acid derivatives of high boiling points are chosen for this application. The absolute rate constants of SmI2 reduction of cinnamic acid in the presence of hexamethyl phosphoramide or t-butanol is considered as a suitable proton source in this reaction. The rates are dependent on substrates and additives as: Rate · [t-BuOH][Cinnamic acid] and Rate · [HMPA][Cinnamic acid] The reduction rates of α-methylcinnamic acid, 2-methylcinnamic acid, 4-methylcinnamic acid, 2-methoxycinnamic acid, 3-methoxycinnamic acid, 4-methoxycinnamic acid, 2-hydroxycinnamic acid, 3-hydroxycinnamic acid, 4-hydroxycinnamic acid, 2-chlorocinnamic acid, 3-chlorocinnamic acid, 4-chlorocinnamic acid were carefully measured to study the substituent effect.
- Lin, Tzuen-Yeuan,Fuh, Ming-Ren,Tsau, Chi-Yu
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- Efficient synthesis and resolution of novel 2-(hydroxymethyl)-7,8-dihydro- 1H-indeno[5,4-b] furan-6(2H)-one by lipase Pseudomonas cepacia
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Lipase Pseudomonas cepacia catalyzed acylation of (±)-2- (hydroxymethyl)-7,8-dihydro-1H-indeno[5,4-b] furan-6(2H)-one using vinyl acetate as the acyl donor in acetone gave (-)-(R)-2-acetoxy-2-(methyl)-7,8-dihydro-1H- indeno[5,4-b] furan-6(2H)-one and (+)-(S)-2-(hydroxymethyl)-7,8-dihydro-1H- indeno[5,4-b] furan-6(2H)-one with high enantiomeric excess. Enantiomerically pure 2-(hydroxymethyl)-7,8-dihydro-1H-indeno[5,4-b] furan-6(2H)-one are useful intermediates for the preparation of Ramelteon, an FDA approved drug for the treatment of insomnia.
- Nagarapu, Lingaiah,Vulupala, Hanmanth Reddy,Bantu, Rajashaker,Sajja, Yashodakrishna,Nanubolu, Jagadeesh Babu
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- Siloxyl ether functionalized resins for chemoselective enrichment of carboxylic acids
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Although the carboxylic acid moiety is prevalent in many biologically produced molecules, including natural products and proteins, methods to chemoselectively target this functional group have remained elusive. Generally, strategies that utilize carboxylate nucleophilicity also promote reactions with other nucleophiles such as amines and hydroxyls. A reagent was sought to facilitate the selective isolation of carboxylic acid containing compounds from complex mixtures. Here, the development of siloxyl ether functionalized solid supports is described.
- Trader, Darci J.,Carlson, Erin E.
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- Electrochemical hydrogenation of 3-(methoxyphenyl)propenoic acids
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Electrosynthesis can successfully be used for double bond hydrogenation in 3-(methoxyphenyl)propenoic acids. The corresponding 3-(methoxyphenyl)propanoic acids were produced in a virtually quantitative yield under the conditions of both electrocatalytic hydrogenation at the Ni cathode modified by electrodeposited dispersed nickel in a DMF-H2O mixture in the presence of AcOH and direct electroreduction using mercury and glassycarbon cathodes in DMF with Bu4NClO4 as the supporting electrolyte, although the mechanisms of these processes are different.
- Korotaeva,Rubinskaya,Rybakova,Gultyai
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- Xylochemistry - Making Natural Products Entirely from Wood
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The first total synthesis of the dimeric berberine alkaloid ilicifoline (ilicifoline B) is reported. Its carbon skeleton is constructed from ferulic acid, veratrole, and methanol. The synthesis reported herein employs starting materials solely derived from wood. The natural product is thus constructed entirely from renewable resources. The same strategy is applied to a formal total synthesis of morphinan alkaloids. The use of wood-derived building blocks (xylochemicals) instead of the conventional petrochemicals represents a sustainable alternative to classical synthetic approaches.
- Stubba, Daniel,Lahm, Günther,Geffe, Mario,Runyon, Jason W.,Arduengo, Anthony J.,Opatz, Till
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- Kinetics-Driven Drug Design Strategy for Next-Generation Acetylcholinesterase Inhibitors to Clinical Candidate
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The acetylcholinesterase (AChE) inhibitors remain key therapeutic drugs for the treatment of Alzheimer's disease (AD). However, the low-safety window limits their maximum therapeutic benefits. Here, a novel kinetics-driven drug design strategy was employed to discover new-generation AChE inhibitors that possess a longer drug-target residence time and exhibit a larger safety window. After detailed investigations, compound 12 was identified as a highly potent, highly selective, orally bioavailable, and brain preferentially distributed AChE inhibitor. Moreover, it significantly ameliorated cognitive impairments in different mouse models with a lower effective dose than donepezil. The X-ray structure of the cocrystal complex provided a precise binding mode between 12 and AChE. Besides, the data from the phase I trials demonstrated that 12 had good safety, tolerance, and pharmacokinetic profiles at all preset doses in healthy volunteers, providing a solid basis for its further investigation in phase II trials for the treatment of AD.
- Zhou, Yu,Fu, Yan,Yin, Wanchao,Li, Jian,Wang, Wei,Bai, Fang,Xu, Shengtao,Gong, Qi,Peng, Tao,Hong, Yu,Zhang, Dong,Zhang, Dan,Liu, Qiufeng,Xu, Yechun,Xu, H. Eric,Zhang, Haiyan,Jiang, Hualiang,Liu, Hong
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p. 1844 - 1855
(2021/03/01)
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- Aldehyde as a Traceless Directing Group for Regioselective C-H Alkylation Catalyzed by Rhodium(III) in Air
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The aromatic aldehyde as a traceless directing group for the regionselective C-H alkylation catalyzed by rhodium(III) under aerobic atmospheric conditions has been developed. The process involves an aldehyde assisted direct addition of C-H bond to unsaturated electrophiles of acrylates or acrylic acids, and the subsequent decarbonylation. A trace amount of water is found to favor the reaction.
- Chen, Si-Qi,Fan, Juan,Li, Chao-Jun,Li, Xin-Ran,Liu, Zhong-Wen,Shi, Xian-Ying
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supporting information
p. 1259 - 1264
(2020/03/13)
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- Synthesis method of succinic acid derivative or 3 -arylpropionic acid (by machine translation)
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The invention discloses a synthesis method of a succinic acid derivative or 3 -arylpropionic acid, which comprises the following steps: adding a base in a drying reaction tube and CO removing CO. 2 The reaction is carried out under the irradiation of visible light, the reaction is carried out under visible light irradiation, and then separation and purification are carried out to obtain the butanedioic acid derivative or 3 -arylpropionic acid product; the base comprises sodium tert-butoxide, potassium tert-butoxide, lithium tert-butyl alcohol and 4 - potassium carbonate; and the reaction substrate comprises an acrylate compound or an aryl vinyl compound. CO can be induced by visible light. 2 The scheme provided by the invention is mild in reaction condition and wide in reaction 3 - substrate selectivity, and the reaction substrate is wide in selectivity, the raw materials are cheap and easily available, and the method has a good industrial application prospect. (by machine translation)
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Paragraph 0101-0114; 0115; 0130
(2020/10/30)
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- Design, synthesis and biological evaluation of novel 1H-1,2,4-triazole, benzothiazole and indazole-based derivatives as potent FGFR1 inhibitors viafragment-based virtual screening
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Fibroblast growth-factor receptor (FGFR) is a potential target for cancer therapy. We designed three novel series of FGFR1 inhibitors bearing indazole, benzothiazole, and 1H-1,2,4-triazole scaffold via fragment-based virtual screening. All the newly synthesised compounds were evaluated in vitro for their inhibitory activities against FGFR1. Compound 9d bearing an indazole scaffold was first identified as a hit compound, with excellent kinase inhibitory activity (IC50 = 15.0 nM) and modest anti-proliferative activity (IC50 = 785.8 nM). Through two rounds of optimisation, the indazole derivative 9 u stood out as the most potent FGFR1 inhibitors with the best enzyme inhibitory activity (IC50 = 3.3 nM) and cellular activity (IC50 = 468.2 nM). Moreover, 9 u also exhibited good kinase selectivity. In addition, molecular docking study was performed to investigate the binding mode between target compounds and FGFR1.
- Liu, Jian,Wen, Yu,Gao, Lina,Gao, Liang,He, Fengjun,Zhou, Jingxian,Wang, Junwei,Dai, Rupeng,Chen, Xiaojing,Kang, Di,Hu, Lihong
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- Synthetic and Mechanistic Studies on 2,3-Dihydrobenzo[ b ][1,4]-oxaselenines Formation from Selenocyanates
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An expedient preparation of selenium-containing hetero-cycles via an m -chloroperbenzoic acid-mediated seleno-annulation starting from selenocyanate derivatives is described. In spite of its significance, this cyclization reaction is virtually understudied not only from the point of view of its scope, but also from the mechanistic aspects associated to this remarkable transformation. In this sense, several selenocyanate and thiocyanate derivatives bearing an aromatic ring were evaluated as substrates under different reaction conditions of this interesting cyclization yielding important insights on its scope as well as relevant information on the reaction mechanism.
- Bonesi, Sergio M.,Cattaneo, Mauricio,Chao, María N.,Rodriguez, Juan B.,Sanchez Gonzalez, Jonathan,Szajnman, Sergio H.
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p. 1643 - 1658
(2020/05/25)
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- Site-Selective, Remote sp3 C?H Carboxylation Enabled by the Merger of Photoredox and Nickel Catalysis
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A photoinduced carboxylation of alkyl halides with CO2 at remote sp3 C?H sites enabled by the merger of photoredox and Ni catalysis is described. This protocol features a predictable reactivity and site selectivity that can be modulated by the ligand backbone. Preliminary studies reinforce a rationale based on a dynamic displacement of the catalyst throughout the alkyl side chain.
- Sahoo, Basudev,Bellotti, Peter,Juliá-Hernández, Francisco,Meng, Qing-Yuan,Crespi, Stefano,K?nig, Burkhard,Martin, Ruben
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supporting information
p. 9001 - 9005
(2019/06/24)
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- Regioselectivity inversion tuned by iron(iii) salts in palladium-catalyzed carbonylations
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Impactful regioselectivity control is crucial for cost-effective chemical synthesis. By using cheap and abundant iron(iii) salts, the hydroxycarbonylations of both aromatic and aliphatic alkenes were significantly enhanced in both reactivity and selectivity (iso/n or n/iso up to >99:1). Moreover, Pd-catalyzed carbonylation selectivity can be switched from branched to linear by using different Fe(iii) salts. In addition, similar results were obtained for the carbonylation of secondary alcohols.
- Huang, Zijun,Cheng, Yazhe,Chen, Xipeng,Wang, Hui-Fang,Du, Chen-Xia,Li, Yuehui
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supporting information
p. 3967 - 3970
(2018/04/23)
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- Ligand-Controlled Regioselective Hydrocarboxylation of Styrenes with CO2 by Combining Visible Light and Nickel Catalysis
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The ligand-controlled Markovnikov and anti-Markovnikov hydrocarboxylation of styrenes with atmospheric pressure of CO2 at room temperature using dual visible-light-nickel catalysis has been developed. In the presence of neocuproine as ligand, the Markovnikov product is obtained exclusively, while employing 1,4-bis(diphenylphosphino)butane (dppb) as the ligand favors the formation of the anti-Markovnikov product. A range of functional groups and electron-poor, -neutral, as well as electron-rich styrene derivatives are tolerated by the reaction, providing the desired products in moderate to good yields. Preliminary mechanistic investigations indicate the generation of a nickel hydride (H-NiII) intermediate, which subsequently adds irreversibly to styrenes.
- Meng, Qing-Yuan,Wang, Shun,Huff, Gregory S.,Konig, Burkhard
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supporting information
p. 3198 - 3201
(2018/03/13)
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- BENZOCYCLOOCTENE-BASED AND INDENE-BASED ANTICANCER AGENTS
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Benzocyclooctene (fused 6,8 ring system) analogues and corresponding indene (fused 6,5 ring system) analogues function as inhibitors of tubulin polymerization. The compounds are useful as anticancer agents in a new therapeutic approach for cancer treatment utilizing small-molecule inhibitors of tubulin polymerization that also act as vascular disrupting agents (VDAs).
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Paragraph 0094
(2018/02/27)
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- A Ligand-Directed Catalytic Regioselective Hydrocarboxylation of Aryl Olefins with Pd and Formic Acid
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An effective Pd-catalyzed hydrocarboxylation of aryl olefins with Ac2O and formic acid is described. A variety of 2- and 3-arylpropanoic acids can be regioselectively formed by the judicious choice of ligand without the use of toxic CO gas.
- Liu, Wei,Ren, Wenlong,Li, Jingfu,Shi, Yuan,Chang, Wenju,Shi, Yian
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supporting information
p. 1748 - 1751
(2017/04/11)
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- Pd-Catalyzed β-C(sp3)?H Arylation of Propionic Acid and Related Aliphatic Acids
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A generally applicable Pd-catalyzed protocol for the β-C(sp3)?H arylation of propionic acid and related α-branched aliphatic acids is reported. Enabled by the use of N-acetyl-β-alanine as ligand our protocol delivers a broad range of arylation products. Notably, the highly challenging substrate, propionic acid, which lacks any acceleration through the Thorpe–Ingold effect, can be employed as substrate with synthetically useful yields. Furthermore, the scalability and synthetic applicability of the protocol are demonstrated.
- Ghosh, Kiron K.,van Gemmeren, Manuel
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supporting information
p. 17697 - 17700
(2017/12/07)
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- Synthesis and biological evaluation of benzocyclooctene-based and indene-based anticancer agents that function as inhibitors of tubulin polymerization
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The natural products colchicine and combretastatin A-4 (CA4) have been inspirational for the design and synthesis of structurally related analogues and spin-off compounds as inhibitors of tubulin polymerization. The discovery that a water-soluble phosphate prodrug salt of CA4 (referred to as CA4P) is capable of imparting profound and selective damage to tumor-associated blood vessels paved the way for the development of a new therapeutic approach for cancer treatment utilizing small-molecule inhibitors of tubulin polymerization that also act as vascular disrupting agents (VDAs). Combination of salient structural features associated with colchicine and CA4 led to the design and synthesis of a variety of fused aryl-cycloalkyl and aryl-heterocyclic compounds that function as inhibitors of tubulin polymerization. Prominent among these compounds is a benzosuberene analogue (referred to as KGP18), which demonstrates sub-nM cytotoxicity against human cancer cell lines and functions (when administered as a water-soluble prodrug salt) as a VDA in mouse models. Structure activity relationship considerations led to the evaluation of benzocyclooctyl [6,8 fused] and indene [6,5 fused] ring systems. Four benzocyclooctene and four indene analogues were prepared and evaluated biologically. Three of the benzocyclooctene analogues were active as inhibitors of tubulin polymerization (IC50 50 = 11 μM) with reduced potency. The most potent inhibitor of tubulin polymerization from this group was benzocyclooctene analogue 23, and it was converted to its water-soluble prodrug salt 24 to assess its potential as a VDA. Preliminary in vivo studies, which utilized the MCF7-luc-GFP-mCherry breast tumor in a SCID mouse model, demonstrated that treatment with 24 (120 mg kg?1) resulted in significant vascular shutdown, as evidenced by bioluminescence imaging at 4 h post administration, and that the effect continued at both 24 and 48 h. Contemporaneous studies with CA4P, a clinically relevant VDA, were carried out as a positive control.
- Herdman, Christine A.,Strecker, Tracy E.,Tanpure, Rajendra P.,Chen, Zhi,Winters, Alex,Gerberich, Jeni,Liu, Li,Hamel, Ernest,Mason, Ralph P.,Chaplin, David J.,Trawick, Mary Lynn,Pinney, Kevin G.
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supporting information
p. 2418 - 2427
(2016/12/18)
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- A biocompatible alkene hydrogenation merges organic synthesis with microbial metabolism
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Organic chemists and metabolic engineers use orthogonal technologies to construct essential small molecules such as pharmaceuticals and commodity chemicals. While chemists have leveraged the unique capabilities of biological catalysts for small-molecule production, metabolic engineers have not likewise integrated reactions from organic synthesis with the metabolism of living organisms. Reported herein is a method for alkene hydrogenation which utilizes a palladium catalyst and hydrogen gas generated directly by a living microorganism. This biocompatible transformation, which requires both catalyst and microbe, and can be used on a preparative scale, represents a new strategy for chemical synthesis that combines organic chemistry and metabolic engineering. Reduction to practice: A hydrogenation reaction has been developed that employs hydrogen generated in situ by a microorganism and a biocompatible palladium catalyst to reduce alkenes on a synthetically useful scale. This type of transformation, which directly combines tools from organic chemistry with the metabolism of a living organism for small-molecule production, represents a new strategy for chemical synthesis.
- Sirasani, Gopal,Tong, Liuchuan,Balskus, Emily P.
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supporting information
p. 7785 - 7788
(2014/08/05)
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- Synthesis and antitumor activity evaluation of 2-arylisoquinoline-1,3(2H, 4H)-diones in vitro and in vivo
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Six 2-(2-acylaminobenzothiazol-6-yl)isoquinoline-1,3(2H,4H)-diones (1a-1f) and five 2-arylisoquinoline-1,3(2H,4H)-diones (1g-1k) were synthesized by refluxing homophthalic anhydrides with 2-acylaminobenzothiazolyl-6-amine or substituted aniline in glacial acetic acid. The cytotoxic activities of 1a-1k were evaluated via MTT method against A431, A549, and PC3. Compound 1b relatively displayed a higher cytotoxic activity than the others. The antitumor effect of 1b were evaluated in established nude mice PANC-1 xenograft model. The results suggest that compound 1b could potentially inhibit tumor growth.
- Kang, Bo-Rui,Wang, Juan,Li, Huan,Li, Yan,Mei, Qi-Bing,Zhang, San-Qi
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p. 1340 - 1349
(2014/03/21)
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- Synthesis and in vitro evaluation of human FP-receptor selective prostaglandin analogues
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The in vitro evaluation of a series of saturated prostaglandins revealed that compounds with omega chin aromatic rings retain nanomolar potency for the human prostaglandin F receptor (hFP receptor), exemplified by compound 8. In contrast, the double bonds are required for activity in the series with an acyclic omega chain as in PGF(2α). (C) 2000 Published by Elsevier Science Ltd.
- DeLong, Mitchell A.,Amburgey, Jack,Taylor, Cynthia,Wos, John A.,Soper, David L.,Wang, Yili,Hicks, Renee
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p. 1519 - 1522
(2007/10/03)
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- 7α,11β-disubstituted estrogens: Probes for the shape of the ligand binding pocket in the estrogen receptor
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To investigate whether the estrogen receptor accommodates 7α and 11β substituents on estradiol in two subsites or in a single subsite, we have prepared three sets of ligands bearing single (7α or 11β) or double (7α and 11β) substituents and measured their binding affinity. The different behavior of each set precludes a definitive choice, but supports a two subsite model with some limitations.
- Tedesco, Rosanna,Katzenellenbogen, John A.,Napolitano, Elio
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p. 2919 - 2924
(2007/10/03)
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- Intramolecular regioselective insertion into unactivated prochiral carbon-hydrogen bonds with diazoacetates of primary alcohols catalyzed by chiral dirhodium(II) carboxamidates. Highly enantioselective total synthesis of natural lignan lactones
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Intramolecular insertion into unactivated prochiral C-H bonds of 3-aryl-1-propyl diazoacetates catalyzed by dirhodium(II) tetrakis[methyl 1-(3-phenyl propanoyl)imidazolidin-2-one-4(R or S)-carboxylate], Rh2(4R-MPPIM)4 or Rh2(4S-MPPIM)4, occurs in 91-96% ee and with virtually complete regiocontrol for the formation of β-benzyl-γ-butyrolactones. This methodology has been applied to the total synthesis of dibenzylbutyrolactone lignans (-)- and (+)-enterolactone, (-)- and (+)-hinokinin, and (+)-arctigenin from substituted cinnamic acids in 19-27% overall yields. Aryltetralin lignan (+)-isodeoxypodophyllotoxin was prepared from the reactant 3,4-(methylenedioxy)cinnamic acid in 36% yield overall, and the lactone precursor to (+)-isolauricerisinol was formed in 96.5% ee and 23% yield overall. Applications of the chiral Rh2(MPPIM)4 catalysts to fully aliphatic systems resulting in the formation of β-substituted-γ-butyrolactones with high regiocontrol and with 93-96% ee have demonstrated the generality of this methodology. A model that provides accurate predictions of β-substituted-γ-butyrolactone absolute configurations in these asymmetric metal carbene transformations is described.
- Bode,Doyle,Protopopova,Zhou
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p. 9146 - 9155
(2007/10/03)
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- 5,6,11,12-Tetrahydrochrysenes: Synthesis of Rigid Stilbene Systems Designed To Be Fluorescent Ligands for the Estrogen Receptor
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We have prepared a series of tetrahydrochrysenes as fluorescent ligands for the estrogen receptor.The stilbene chromophore in this tetracyclic system is held rigid and is adorned with an electron-donating hydroxyl group at C-8 that corresponds to the phenolic hydroxyl of estrogens and an electron acceptor at C-2 to give a donor-acceptor fluorophore.Additional substituents at C-5 and C-11 provide additional bulk that improves receptor binding affinity without distorting the planar conjugated system.The tetrahydrochrysene core was prepared by an acyloin condensation of α-alkyl m-methoxyhydrocinnamate esters, followed by a double dehydrative cyclization.The cis and trans isomers of the alkyl substituted systems could be separated and their stereochemistry ascertained by X-ray crystallographic analysis; the trans isomer has the higher receptor binding affinity, and the derivative with ethyl substituents at C-5 and C-11 has the best affinity.The donor-acceptor systems were prepared by functional group manipulations on one of the aromatic methoxy groups: conversion to the trifluoromethanesulfonate was followed by a palladium-mediated carbonylation to give the acetyl derivative and methoxycarbonylation to give the ester.The ester was further elaborated to the amide and nitrile.The nitro compound was prepared by nitration of protio system, itself prepared by hydrogenolysis of the trifluoromethanesulfonate.As will be described later, these tetrahydrochrysenes provide a favorable combination of estrogen receptor binding affinity and long wavelength, high quantum yield fluorescence to make them useful as fluorescent ligands for the estrogen receptor.
- Hwang, Kwang-Jin,O'Neil, James P.,Katzenellenbogen, John A.
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p. 1262 - 1271
(2007/10/02)
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- Studies on the Synthesis of 1-Azaspiroundecanes Related to Histrionicotoxin
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3-Methoxybenzaldehyde was converted into 4-(3-methoxyphenyl)butylamine (4), and the derived hydrochloride was reduced with Li/NH3/EtOH to give the spirocyclic keto amine 6.The reduction of 6 and urethane derivatives 13 and 14 to give the corresponding cis and trans alcohols 9/10, 15/16, and 17/18 was studied.The keto amine 6 upon attempted ketalization underwent rearrangement to give the α,β-unsaturated imine 11.Treatment of 6 with N-chlorosuccinimide, followed by DBU, gave the aziridine 21.The amide 25 was converted derectly into 1-azaspiroundecane-2,8-dione (24) by Birch reduction and acid hydrolysis.The dione 24 underwent stereospecific reduction with LS-Selectride to give the cis alcohol 30.
- Venit, John J.,DiPierro, Michael,Magnus, Philip
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p. 4298 - 4301
(2007/10/02)
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- Furan Derivatives. Part 10. Synthesis of Cycloheptabenzofuran
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Cycloheptabenzofuran 2 was synthesized by heating (5-oxo-5H-benzocyclohepten-4-yloxy)acetic acid 16 with sodium acetate in acetic anhydride or by photocyclization of 16 in acetonitrile.Several reactions of cycloheptabenzofuran 2 were examined.Protonation of 2 with trifluoroacetic acid occurred at the 2-position to give a tropylium ion 17.Catalytic hydrogenation of 2 with palladium on charcoal proceeded smoothly to give tetrahydrocycloheptabenzofuran 18.The Diels-Alder reaction of 2 with tetracyanoethylene produced an adduct 19.Formylation of 2 with phosphorus oxychloride and dimethylformamide occurred easily at the 2-position to afford compound 20.Cycloheptabenzofuran 2 has both properties of heptafulvene and benzofuran.
- Horaguchi, Takaaki,Hasegawa, Eietsu,Shimizu, Takahachi,Tanemura, Kiyoshi,Suzuki, Tsuneo
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p. 365 - 369
(2007/10/02)
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- OXIDATIVE COUPLING. II. THE TOTAL SYNTHESIS OF ENTEROLACTONE
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Oxidative coupling of 3-methoxyhydrocinnamic acid dianion with molecular iodine forms the key step in an efficient synthesis of enterolactone.
- Belletire, J. L.,Fremont, S. L.
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p. 127 - 130
(2007/10/02)
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- Photoreactions of α-sulfonyloxyketones
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Earlier work on the photochemistry of α-sulfonyloxyketones uncovered their propensity to form the corresponding α-ketocarbonium ions on photolysis.Typical reactions such as intramolecular cyclizations, carbonium ion rearrangements, and solvent trapping were found.This paper describes an attempt to extend this reaction to a general synthetic technique for polyene cyclizations.During the course of this work two other major reaction pathways were found.The first is an α-keto carbonium ion to acylium ion rearrangement and the second is a photoreduction-elimination process that leads to an α-keto radical rather than the corresponding cation.
- Charlton, James Leslie.,Lai, Hoi Kiong.,Lypka, Gerald Nicholas
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p. 458 - 462
(2007/10/02)
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- Production of unsaturated carbocyclic ketones
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Preparation of α,β-unsaturated carbocyclic ketones by reacting an enol lactone with a carbanion generated by treatment of a methylphosphonate or a mono-substituted methylphosphonate with base.
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