- Intramolecular pyridone/enyne photocycloaddition: Partitioning of the [4 + 4] and [2 + 2] pathways
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Chemical equations presented. Intramolecular photocycloaddition (>290 nm) between a 1,3-enyne and a 2-pyridone is far more selective than the intermolecular version; a three-atom linkage both controls regiochemistry and separates the [2 + 2] and [4 + 4] pathways. All four head-to-head, head-to-tail, tail-to-head, and tail-to-tail tetherings have been investigated. Linkage via the ene of the enyne leads to [2 + 2] products regardless of alkene geometry, whereas linkage through the yne results in [4 + 4] cycloadducts. The bridged 1,2,5-cyclooctatriene products of [4 + 4] cycloaddition are unstable and undergo a subsequent [2 + 2] dimerization reaction.
- Kulyk, Svitlana,Dougherty, William G.,Kassel, W. Scott,Zdilla, Michael J.,Sieburth, Scott M.
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- Total synthesis of paracentrone, C31-allenic opo-carotenoid
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The stereocontrolled total synthesis of a C31-allenic apocarotenoid, paracentrone, was achieved by the convergent C20 + C11 = C31 strategy. The key elements of our synthesis were the Pd-catalyzed cross-coupling to stereoselectively construct the conjugated polyene backbone skeleton and the designed geometrical isomerization at the central double bond of the conjugated polyene chain. In addition, the terminal oxygenated cyclohexane ring having the allenic moiety was prepared by the highly diastereoselective Sharpless epoxidation under our own reaction conditions. The Royal Society of Chemistry 2005.
- Murakami, Yusuke,Nakano, Masayuki,Shimofusa, Takuya,Furuichi, Noriyuki,Katsumura, Shigeo
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- P(MeNCH2CH2)3N: An efficient catalyst for the desilylation of tert- butyldimethylsilyl ethers
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tert-Butyldimethylsilyl (TBDMS) ethers of primary, secondary, and tertiary alcohols and phenolic TBDMS ethers are desilylated to their corresponding alcohols and phenols, respectively, in DMSO, at 80 °C, in 68- 94% yield in the presence of 0.2-0.4 equiv of P(MeNCH2CH2)3N. Using P(i- PrNCH2CH2)3N as the catalyst, 85-97% yields of desilylated alcohols were obtained from TBDMS ethers of 1-octanol, 2-phenoxyethanol, and racemic α- phenyl ethanol. These are the first examples of desilylations of silyl ethers catalyzed by nonionic bases. Both catalysts were much less effective for the desilylation of tert-butyldiphenylsilyl (TBDPS) ethers (22-45% yield) under the same conditions as used for TBDMS ethers. Possible pathways involving nucleophilic attack of the anion of the solvent molecule (generated by the catalyst) at the Si-O bond of silyl ether or a prior activation of the silyl ether by the catalyst via a P-Si interaction followed by nucleophilic attack of the solvent anion are proposed on the basis of 1H and 31P NMR experimental data.
- Yu, Zhengkun,Verkade, John G.
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Read Online
- Synthesis of C6 acetylenic alcohols
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C6 acetylenic alcohols are important intermediates in the synthesis of Vitamin A and carotenoids. New synthesis methods of the C6 acetylenic alcohols and their four derivatives are reported. These designed synthesis methods are useful improvement to the present methodologies. Structures of these compounds are confirmed by 1H NMR, IR and mass spectra analysis.
- Pu, Shuai,Zhang, A.I. Gui,Zhang, Shao Feng,Wang, Y.U. Liang
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- Chiral 1,2,3-Triazolium Salt Catalyzed Asymmetric Mono- and Dialkylation of 2,5-Diketopiperazines with the Construction of Tetrasubstituted Carbon Centers
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Novel asymmetric mono- and dialkylation reactions of α-substituted 2,5-diketopiperazines catalyzed by new chiral spirocyclic-amide-derived triazolium organocatalysts have been developed, resulting in a range of enantioenriched 2,5-diketopiperazine derivatives containing one or two tetrasubstituted carbon stereocenters. The reactions feature high yields (up to 98%), and excellent cis-diastereo- and enantioselectivities (up to >20:1 dr, >99 % ee), and they provide a new asymmetric synthetic approach to important functionalized 2,5-diketopiperazine skeletons. Furthermore, a possible reaction mechanism was proposed based on both control experiments and extensive DFT calculations.
- Yang, Ju-Song,Lu, Ka,Li, Chen-Xiao,Zhao, Zu-Hang,Zhang, Xiao-Ming,Zhang, Fu-Min,Tu, Yong-Qiang
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supporting information
(2022/01/22)
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- Atom-Economical Cross-Coupling of Internal and Terminal Alkynes to Access 1,3-Enynes
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Selective carbon-carbon (C-C) bond formation in chemical synthesis generally requires prefunctionalized building blocks. However, the requisite prefunctionalization steps undermine the overall efficiency of synthetic sequences that rely on such reactions, which is particularly problematic in large-scale applications, such as in the commercial production of pharmaceuticals. Herein, we describe a selective and catalytic method for synthesizing 1,3-enynes without prefunctionalized building blocks. In this transformation several classes of unactivated internal acceptor alkynes can be coupled with terminal donor alkynes to deliver 1,3-enynes in a highly regio- and stereoselective manner. The scope of compatible acceptor alkynes includes propargyl alcohols, (homo)propargyl amine derivatives, and (homo)propargyl carboxamides. This method is facilitated by a tailored P,N-ligand that enables regioselective addition and suppresses secondary E/Z-isomerization of the product. The reaction is scalable and can operate effectively with as low as 0.5 mol % catalyst loading. The products are versatile intermediates that can participate in various downstream transformations. We also present preliminary mechanistic experiments that are consistent with a redox-neutral Pd(II) catalytic cycle.
- Liu, Mingyu,Tang, Tianhua,Apolinar, Omar,Matsuura, Rei,Busacca, Carl A.,Qu, Bo,Fandrick, Daniel R.,Zatolochnaya, Olga V.,Senanayake, Chris H.,Song, Jinhua J.,Engle, Keary M.
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supporting information
p. 3881 - 3888
(2021/04/06)
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- Synthetic study of an intermediate towards paracentrone
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Paracentrone (1), the second naturally occurring C31-methyl ketone apocarotenoid from fucoxanthin (2), was first isolated from the sea urchin Paracentrotus lividus. In this study, we focused on this carotenoid metabolite and report on a synthetic approach towards (3E)-(5R)-[(2R,4S)-2-hydroxy-4-(tert-butyldimethylsilyl)oxy-2,6,6-trimethylcyclohexylidene]-1-iodo-4-methyl-1,3, 5-hexatriene (5), a synthetic intermediate towards 1. This was obtained from epoxy acetylene (11) via (2E)-(4R)-[(2R,4S)-2-hydroxy-4-(tert-butyldimethyl-silyl)oxy-2,6,6-trimethylcyclohexylidene]-3-methylpenta-2,4-dien-1-ol (7).
- Kaneyama, Taiki,Fujimaru, Kazumi,Takemura, Mami,Hasegawa, Kizuku,Hamada, Masahiro,Kishimoto, Takao,Urabe, Daisuke,Nakajima, Noriyuki
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p. 281 - 294
(2019/08/01)
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- Chemoenzymatic one-pot reaction of noncompatible catalysts: Combining enzymatic ester hydrolysis with Cu(i)/bipyridine catalyzed oxidation in aqueous medium
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The combination of chemical catalysts and biocatalysts in a one-pot reaction has attracted considerable interest in the past years. However, since each catalyst requires very different reaction conditions, chemoenzymatic one-pot reactions in aqueous media remain challenging and are limited today to metal-catalysts that display high activity in aqueous media. Here, we report the first combination of two incompatible catalytic systems, a lipase based ester hydrolysis with a water-sensitive Cu/bipyridine catalyzed oxidation reaction, in a one-pot reaction in aqueous medium (PBS buffer). Key to the solution was the compartmentalization of the Cu/bipyridine catalyst in a core-shell like nanoparticle. We show the synthesis and characterization of the Cu/bipyridine functionalized nanoparticles and the application in the oxidation of allylic and benzylic alcohols in aqueous media. Furthermore, the work demonstrates the implementation of a one-pot reaction process with optimized reaction conditions involving a lipase (CAL-B) to hydrolyze various acetate ester substrates in the first step, followed by oxidation of the resulting alcohols to the corresponding aldehydes under aerobic conditions in aqueous media.
- Sand, Henning,Weberskirch, Ralf
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p. 33614 - 33626
(2017/07/12)
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- Extrapolation of the gold-catalyzed cycloisomerization to the palladium-catalyzed cross-coupling/cycloisomerization of acetylenic alcohols for the synthesis of polysubstituted furans: Scope and application to tandem processes
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This paper describes the development of an integrated approach for the preparation of diverse furan derivatives from acetylenic alcohols by gold and palladium catalyzed π-activation chemistry. Notably, this new method was found to be amenable to cycloocty
- Praveen, Chandrasekar,Perumal, Paramasivan T.
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p. 288 - 299
(2016/02/23)
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- Discovery of a Potent Free Fatty Acid 1 Receptor Agonist with Low Lipophilicity, Low Polar Surface Area, and Robust in Vivo Efficacy
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The free fatty acid receptor 1 (FFA1 or GPR40) is established as an interesting potential target for treatment of type 2 diabetes. However, to obtain optimal ligands, it may be necessary to limit both lipophilicity and polar surface area, translating to a need for small compounds. We here describe the identification of 24, a potent FFA1 agonist with low lipophilicity and very high ligand efficiency that exhibit robust glucose lowering effect.
- Hansen, Steffen V. F.,Christiansen, Elisabeth,Urban, Christian,Hudson, Brian D.,Stocker, Claire J.,Due-Hansen, Maria E.,Wargent, Ed T.,Shimpukade, Bharat,Almeida, Reinaldo,Ejsing, Christer S.,Cawthorne, Michael A.,Kassack, Matthias U.,Milligan, Graeme,Ulven, Trond
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supporting information
p. 2841 - 2846
(2016/04/10)
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- A method of product yield allylol cis
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The invention relates to a method for improving the yield of an allyl alcohol maleinoid form product, the formula (1) are isomerized into a mixture of the formula (2) and the formula (3), the formula (1), the formula (2) and the formula (3) are selected from alkyl, aryl and alkaryl, R2 is selected from H, alkyl and aryl, in a solvent and with the existence of a heterogeeous acid catalyst, the formula (1) is subjected to reaction, the solvent is water or a multiphase solvent system which comprises an aqueous phase and an organic solvent phase, and the organic solvent phase comprises an organic solvent which is selected from ethers, ketone or saturated fat hydrocarbon or a mixture of the same and is unmixed with water, the formula (1) is subjected to allylic rearrangement reaction, and a certain proportion of formula (3) is added into the allylic rearrangement reaction system of the formula (1); the gaseous phase interior label content of the formula (3) is greater than 95%. According to the invention, the forming of the product maleinoid form (2) is facilitated, the proportion of the maleinoid form (2) to the transform (3) is enhanced, and the yield of the maleinoid form (2) can be improved by about 13% compared with an original system.
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Paragraph 0030-0032
(2017/03/17)
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- Ruthenium-catalyzed functionalization of pyrroles and indoles with propargyl alcohols
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Several ruthenium-catalyzed atom-economic transformations of propargyl alcohols with pyrroles or indoles leading to alkylated, propargylated, or annulated heteroaromatics are reported. The mechanistically distinct reactions are catalyzed by a single ruthenium(0) complex containing a redox-coupled dienone ligand. The mode of activation regarding the propargyl alcohols determines the reaction pathway and depends on the alcohols' substitution pattern. Secondary substrates form alkenyl complexes by a 1,2-hydrogen shift, whereas the transformation of tertiary substrates involves allenylidene intermediates. 1-Vinyl propargyl alcohols are converted by a cascade allylation/cyclization sequence. The environmentally benign processes are of broad scope and allow the selective synthesis of highly functionalized pyrroles and indoles generating water as the only waste product. Copyright
- Thies, Nora,Hrib, Cristian G.,Haak, Edgar
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supporting information; experimental part
p. 6302 - 6308
(2012/06/18)
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- Ruthenium-catalyzed allylation-cyclization reactions of cyclic 1,3-dicarbonyl compounds with 1-vinyl propargyl alcohols
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Ruthenium-catalyzed allylation-cyclization reactions of cyclic 1,3-dicarbonyl compounds with 1-vinyl propargyl alcohols that lead to diverse carbo- or heterocyclic products in a one-pot cascade process are reported. These mechanistically distinct reactions are catalyzed by a single ruthenium(0) complex that contains a redox-coupled dienone ligand. The reaction pathway strongly depends on the substrate substitution pattern, which determines the mode of activation of the 1-vinyl propargyl alcohol. The environmentally benign process, which generates water as the only waste product, is of wide scope and allows the atom-economic synthesis of highly functionalized furans, pyrans, and spirocarbocycles. Ring-producing expert: Ru complexes of redox-coupled cyclopentadienone ligands catalyze various allylation-cyclization reactions of cyclic 1,3-dicarbonyl compounds with 1-vinyl propargyl alcohols through strikingly distinct modes of activation to afford highly functionalized furans, pyrans, and spirocarbocycles (see scheme). Copyright
- Jonek, Anita,Berger, Stefanie,Haak, Edgar
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p. 15504 - 15511
(2013/01/15)
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- ORTHO-FLUORO SUBSTITUTED COMPOUNDS FOR THE TREATMENT OF METABOLIC DISEASES
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There is provided novel fluoro-substituted compounds capable of modulating the G- protein-coupled receptor GPR40, compositions comprising the compounds, and methods for their use for controlling insulin levels in vivo and for the treatment of conditions such as type II diabetes, hypertension, ketoacidosis, obesity, glucose intolerance, and hypercholesterolemia and related disorders associated with abnormally high or low plasma lipoprotein, triglyceride or glucose levels.
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Page/Page column 46-47
(2012/10/18)
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- An asymmetric total synthesis of brevisamide
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An enantioselective synthesis of marine alkaloid brevisamide was accomplished in a convergent manner. The synthesis utilized an enantioselective hetero-Diels - Alder reaction which sets three chiral centers in compound 11. The synthesis also features a modified Wolff-Kishner reduction, Rubottom oxidation, and Suzuki - Miyaura coupling to furnish brevisamide.
- Ghosh, Arun K.,Li, Jianfeng
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supporting information; experimental part
p. 4164 - 4167
(2009/12/31)
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- PHOTOCHEMICAL ISOMERIZATION OF A PENT-2-EN-4-YN-1-OL
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The present invention relates to a process for photochemically isomerizing an E-pent-2-en-4-yn-1-ol to a Z-pent-2-en-4-yn-1-ol and vice versa.
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Page/Page column 7-8
(2009/07/25)
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- Anodic oxidation: An attractive alternative to CAN-mediated cleavage of para-methoxyphenyl ethers
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para-Methoxyphenyl (PMP) ether is a very convenient protecting group for the alcohol function; however, its cleavage requires strong oxidative conditions. In this field, the use of powerful eerie ammonium nitrate has been widely described, despite the fac
- Vaxelaire, Carine,Souquet, Florence,Lannou, Marie-Isabelle,Ardisson, Janick,Royer, Jacques
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supporting information; experimental part
p. 3138 - 3140
(2009/12/05)
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- Total synthesis and structural confirmation of brevisamide, a new marine cyclic ether alkaloid from the dinoflagellate Karenia brevis
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The first total synthesis of brevisamide (1) has been accomplished in 21 linear steps starting from cis-but-2-ene-1,4-diol. A synthetic highlight is the Suzuki-Miyaura coupling between an ether ring fragment and a dienol side chain. This result confirmed the structure of 1 isolated from the dinoflagellate Karenia brevis.
- Kuranaga, Takefumi,Shirai, Tomohiro,Baden, Daniel G.,Wright, Jeffrey L. C.,Satake, Masayuki,Tachibana, Kazuo
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supporting information; experimental part
p. 217 - 220
(2009/06/20)
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- Process for the rearrangement of allyl alcohols
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The present invention is directed to a process for isomerizing a pent-1-en-3-ol according to formula (1) to a mixture of the stereoisomers Z-pent-2-en-1-ol (2) and E-pent-2-en-1-ol (3) according to formulae (2) and (3) wherein R1 is selected from alkyl, aryl, and alkylaryl radicals, R2 is selected from H, alkyl, and aryl radicals; which process comprises reacting the pent-1-en-3-ol (1) in a solvent and in the presence of a heterogeneous acid catalyst. The heterogeneous acid catalyst is preferably selected from the group consisting of Br?nsted acids on a carrier, strong acidic cation exchangers and polymers having acidic groups. The products of the process according to the present invention are important intermediates for the manufacture of isoprenoids such as vitamin A and derivatives thereof and carotenoids.
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Page/Page column 7
(2009/12/23)
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- PROCESS FOR ISOMERIZING A PENT-1-EN-3-OL
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The present invention relates to a process for isomerizing a pent-1-en-3-ol to a mixture of the isomers Z-pent-2-en-1-ol and E-pent-2-en-1-ol by reacting the pent-1-en-3-ol (1) in a multiphase system comprising an aqueous phase and an organic solvent phase, and in the presence of an acid catalyst which is not a cation exchanger, wherein the organic solvent phase comprises a water-immiscible organic solvent.
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(2008/12/08)
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- Synthesis of pluraflavin A "aglycone"
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The "aglycone" of pluraflavin A (2) has been synthesized. The key features of this synthesis include a 1,3-dipolar cycloaddition between a nitrile oxide (cf. 14) and an olefin (22) to yield an isoxazoline followed by subsequent conversion into the γ-pyrone of pluraflavin A. The epoxide moiety linked to the pyrone is installed prior to Diels-Alder installation of the D ring, which allows access to a number of potentially active cytotoxic intermediates en route to the final compound. The preliminary in vitro results of two such compounds are also included with the racemic title compound exhibiting cytotoxicity in the nanomolar range.
- Wright, Benjamin J. D.,Hartung, John,Peng, Feng,Van De Water, Ryan,Liu, Haibo,Tan, Quen-Hui,Chou, Ting-Chao,Danishefsky, Samuel J.
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supporting information; experimental part
p. 16786 - 16790
(2009/04/14)
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- Catalytic isomerization of Z-pentol to E-pentol
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A process for catalytically isomerizing Z-3-methylpent-2-en-4-yn-1-ol to E-3-methylpent-2-en-4-yn-1-ol is provided. This process includes contacting a stereoisomeric mixture containing Z-3-methylpent-2-en-4-yn-1-ol and E-3-methylpent-2-en-4-yn-1-ol with a source of bromine radicals in a two-phase reaction mixture having an aqueous phase and a stereoisomeric mixture phase, intermixing the reaction mixture, and heating the reaction mixture to a temperature from about ?10° C. to about 100° C.
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- Isomerization of a pentol
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In a process for catalytically isomerizing Z-3-methylpent-2-en-4-yn-1-ol to E-3-methylpent-2-en-4-yn-1-ol in a mixture of both these stereoisomers there are employed as the isomerization catalyst bromine radicals and the isomerization is conducted in a two-phase system of an aqueous phase and the stereoisomeric mixture phase, the stereoisomeric mixture optionally being present in an essentially water-immiscible organic solvent, with intermixing of the reaction mixture and at temperatures from about -10°C to about 100°C. The source of the bromine radicals is generally an alkali metal or alkaline earth metal bromide, or ammonium bromide. In one embodiment of the process of the present invention a salt of a heavy metal is used as the catalyst for promoting the generation of bromine radicals from the source thereof, and in addition oxygen is generally used as an auxiliary agent for promoting the bromine radical generation. In a further embodiment there is used as such catalyst a strong peroxide-type oxidizing agent, e.g. an alkali metal or alkaline earth metal peroxomonosulphate, peroxoborate, peroxodisulphate or peroxodiphosphate, or the system hydrogen peroxide/alkali metal or alkaline earth metal sulphate. The stereoisomer produced and isolated in the larger proportion, i.e. Z-pentol, is a useful intermediate, e.g. for the manufacture of vitamin A, and the stereoisomer produced and isolated in the smaller proportion, i.e. E-pentol, is also a useful intermediate, in this case e.g. for the manufacture of astaxanthin, zeaxanthin and further carotenoids.
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- Synthetic studies toward potent cytotoxic agent amphidinolide B: Synthesis of the C8-C18 fragment
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A practical synthesis of the C8-C18 fragment 1 of amphidinolide B is described in which the Stille coupling method was employed to construct the trisubstituted C28=C13-C14=C15 's-cis-1,3-diene' moiety from suitably functionalized vinyl iodide (4) and vinyl stannane (5) fragments, the former being prepared from an acetylene precursor using Negishi's carboalumination/iodination method.
- Chakraborty,Thippeswamy
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p. 150 - 152
(2007/10/03)
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- A general and facile synthesis of substituted furans by palladium- catalyzed cycloisomerization of (Z)-2-en-4-yn-1-ols
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A general and facile synthesis of furans, based on Pd(II)-catalyzed cycloisomerization of (Z)-2-en-4-yn-1-ols, is described. Cycloisomerization reactions are carried out at 25-100 °C in the presence of a very simple catalytic system, consisting of K2PdI4, under essentially neutral conditions. This new methodology is very versatile and can be applied to the synthesis of a variety of substituted furans, including particularly fragile, naturally occurring furans such as rosefuran. Efficient synthetic approaches for the regioselective synthesis of suitably substituted (Z)-2-en-4-yn-1-ols have been developed.
- Gabriele,Salerno,Lauria
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p. 7687 - 7692
(2007/10/03)
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- Versatile synthesis of bicyclo[9.3.1]pentadecatriene for new bicyclic taxoids
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A common carbon skeleton bicyclo[9.3.1]pentadecatriene of taxachitrienes was synthesized in its des-methyl form in short steps. The key step was Nicholas-Hosomi type reaction in the acidic cyclization between ene-yne biscobalthexacarbonyl complex electrophile with allyltrimethylsilane nucleophile. Decomplexation of the biscobalthexacarbonyl was achieved with a tin hydride and NBS in 1,4-cyclohexadiene solvent.
- Shibuya, Satoshi,Isobe, Minoru
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p. 373 - 374
(2007/10/03)
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- Synthesis of a diterpene taxoid skeleton, bicyclo[9.3.1]pentadecatriene
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The synthesis of bicyclo[9.3.1]pentadecatriene skeleton was investigated by employing cyclization reactions using two key precursors bearing acetylene cobalt complex. Cyclization for the synthesis of strained twelve-membered ring was achieved via Nicholas type reaction in reasonable yield. Reductive decomplexation of the dicobalt hexacarbonyl moiety of the cyclization product was achieved with n-Bu3SnH in the presence of a catalytic amount of NBS in 1,4-cyclohexadiene solvent.
- Shibuya, Satoshi,Isobe, Minoru
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p. 6677 - 6698
(2007/10/03)
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- Application of the steric directing group strategy to the stereoselective synthesis of the octahydronaphthalene substructure of kijanolide and tetronolide
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A highly stereoselective synthesis of the kijanolide/tetronolide octahydronaphthalene substructure 4 has been completed. The synthesis proceeds in 16 steps from L-glyceraldehyde acetonide (8), with 88% stereoselectivity and in 11% overall yield. Key steps are the following: (1) the asymmetric crotylborations of 8 and 12 that introduce the C(5), C(6), and C(8) stereocenters of 4; (2) the modified Suzuki coupling of vinylboronic acid 36 and dibromo olefin 31 that establishes the conjugated triene unit and introduces the C(9) Br steric directing group in a single operation; and (3) the highly stereoselective intramolecular Diels-Alder cycloaddition of tetraene 7. Stereochemical information obtained from the intramolecular Diels-Alder reactions of 25 and 26 provides a framework for rationalizing the role of the C(5) acetoxy group and the C(9) Br substituent on the stereoselectivity of the intramolecular Diels-Alder reaction of 7.
- Roush, William R.,Brown, Bradley B.
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p. 2268 - 2278
(2007/10/02)
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