- Synthesis of 2,3-dihydro-1-phenylbenzo[b]phosphole (1-phenylphosphindane) and its use as a mechanistic test in the asymmetric appel reaction: Decisive evidence against involvement of pseudorotation in the stereoselecting step
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Racemic 2,3-dihydro-1-phenylbenzo[b]phosphole was obtained by reduction of 1-phenylbenzo[b]phosphole-1-oxide, itself derived by ring-closing metathesis of phenylstyrylvinylphosphine oxide. The title compound was then reoxidized under asymmetric Appel cond
- Carr, Damien J.,Kudavalli, Jaya Satyanarayana,Dunne, Katherine S.,Mueller-Bunz, Helge,Gilheany, Declan G.
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- Site- and regio-selective incorporation of carbon dioxide into the C(sp2)Si bond of benzosilacyclobutenes
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A reaction of benzosilacyclobutenes with carbon dioxide is catalyzed by a nickel complex having an N-heterocyclic carbene ligand. Carbon dioxide inserts into the C(sp2)Si bond in a site- and regio-selective manner to form a carboncarbon bond, furnishing benzoic acid derivatives.
- Ishida, Naoki,Okumura, Shintaro,Murakami, Masahiro
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- Enantio- and diastereotopos differentiation in the palladium(II)-catalyzed hydrosilylation of bicyclo[2.2.1]alkene scaffolds with silicon-stereogenic silanes
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The palladium(II)-catalyzed hydrosilylation of meso-configured bicyclo[2.2.1]alkene scaffolds proved to be an invaluable model reaction for the development of reagent-controlled asymmetric transformations based on silicon-stereogenic silanes as stereoinducers. In the present investigation, the subtle structural requirements of the silane substitution pattern in enantiotopos-differentiating single hydrosilylations of a norbornene-type substrate are disclosed. Extension of this chemistry to a double hydrosilylation of norbornadiene entails a significant increase in stereochemical complexity. Although differentiation of enantiotopic positions by the chiral reagent is demanded in the first hydrosilylation, the same reagent must then differentiate diastereotopic positions in the second. Remarkably high stereocontrol was found in this double hydrosilylation with several silanes first used in the hydrosilylations of the norbornene-type system. Depending on the enantiomeric purity of the silane, C2- and Cs-symmetric adducts, respectively, were obtained. The identity of the key quaternary silanes was revealed by crystallographic analysis. By this method, the relative and absolute configurations were also assigned, which, in turn, imply that all enantiospecific substitutions at silicon proceed with stereoretention. On the basis of these solid-state structures, we also discuss the structural implications of silane substitution for the diastereoselectivity-determining step of this palladium(II)-catalyzed hydrosilylation reaction. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Rendler, Sebastian,Froehlich, Roland,Keller, Manfred,Oestreich, Martin
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- Bimetal Cooperatively Catalyzed Arylalkynylation of Alkynylsilanes
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An unprecedented Pd/Rh cooperatively catalyzed arylalkynylation of alkynylsilanes was developed to merge an alkynylidene moiety with benzosilacycle. These silaarenes possess a particular aggregation-induced emission behavior. Mechanistic investigations demonstrate that the relay trimetallic transmetalation plays a pivotal role in governing this transformation.
- Chen, Xing,Li, Mengke,Liu, Zhipeng,Yang, Can,Xie, Haisheng,Hu, Xinwei,Su, Shi-Jian,Jiang, Huanfeng,Zeng, Wei
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supporting information
p. 6724 - 6728
(2021/09/08)
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- Synthesis and Structure-Affinity Relationships of Spirocyclic Benzopyrans with Exocyclic Amino Moiety
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σ1 and/or σ2 receptors play a crucial role in pathological conditions such as pain, neurodegenerative disorders, and cancer. A set of spirocyclic cyclohexanes with diverse O-heterocycles and amino moieties (general structure III) was prepared and pharmacologically evaluated. In structure-activity relationships studies, the σ1 receptor affinity and σ1:σ2 selectivity were correlated with the stereochemistry, the kind and substitution pattern of the O-heterocycle, and the substituents at the exocyclic amino moiety. cis-configured 2-benzopyran cis-11b bearing a methoxy group and a tertiary cyclohexylmethylamino moiety showed the highest σ1 affinity (Ki = 1.9 nM) of this series of compounds. In a Ca2+ influx assay, cis-11b behaved as a σ1 antagonist. cis-11b reveals high selectivity over σ2 and opioid receptors. The interactions of the novel σ1 ligands were analyzed on the molecular level using the recently reported X-ray crystal structure of the σ1 receptor protein. The protonated amino moiety forms a persistent salt bridge with E172. The spiro[benzopyran-1,1′-cyclohexane] scaffold and the cyclohexylmethyl moiety occupy two hydrophobic pockets. Exchange of the N-cyclohexylmethyl moiety by a benzyl group led unexpectedly to potent and selective μ-opioid receptor ligands.
- Kronenberg, Elisabeth,Weber, Frauke,Brune, Stefanie,Schepmann, Dirk,Almansa, Carmen,Friedland, Kristina,Laurini, Erik,Pricl, Sabrina,Wünsch, Bernhard
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supporting information
p. 4204 - 4217
(2019/05/06)
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- Highly diastereoselective synthesis of tetralin-fused spirooxindoles via lewis acid-catalyzed C(sp3)H bond functionalization
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A highly diastereoselective synthesis of tetralin-fused spirooxindole derivatives was described. Treatment of benzylidene oxindoles with a catalytic amount of Sc(OTf)3 in refluxing hexane afforded the target compounds in good chemical yields with excellent diastereoselectivities (up to >20:1). Detailed investigation of the reaction mechanism revealed that both interconversion of the two diastereomers and their solubility difference in reaction medium were the key to achieving excellent diastereoselectivities.
- Machida, Mizuki,Mori, Keiji
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p. 868 - 871
(2018/07/03)
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- COMPOUNDS, COMPOSITIONS AND METHODS FOR SYNTHESIS
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The present disclosure, among other things, provides technologies for synthesis, including reagents and methods for stereoselective synthesis. In some embodiments, the present disclosure provides compounds useful as chiral auxiliaries. In some embodiments, the present disclosure provides reagents and methods for oligonucleotide synthesis. In some embodiments, the present disclosure provides reagents and methods for chirally controlled preparation of oligonucleotides. In some embodiments, technologies of the present disclosure are particularly useful for constructing challenging internucleotidic linkages, providing high yields and stereoselectivity.
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Paragraph 001156; 001157; 001158; 001159
(2019/01/10)
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- 9-Silafluorenyl Dichlorides as Chemically Ligating Coupling Agents and Their Application in Peptide Synthesis
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A fundamentally simple, mild, and practical procedure for peptide bond formation is reported that employs a stoichiometric amount of easy-to-access 9-silafluorenyl dichlorides as the coupling agent. Without initial preactivation or elaboration of the carboxylic acid or amine termini of the amino acids, the developed reagent is proposed to act through an unprecedented chemical ligation mechanism, bringing the two coupling partners together before being subsequently eliminated. The desired amides or peptide bonds are thus furnished in good yields and with low to no epimerization.
- Aspin, Samuel J.,Taillemaud, Sylvain,Cyr, Patrick,Charette, André B.
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supporting information
p. 13833 - 13837
(2016/10/26)
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- Scalable anti-Markovnikov hydrobromination of aliphatic and aromatic olefins
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To improve access to a key synthetic intermediate we targeted a direct hydrobromination-Negishi route. Unsurprisingly, the anti-Markovnikov addition of HBr to estragole in the presence of AIBN proved successful. However, even in the absence of an added initiator, anti-Markovnikov addition was observed. Re-examination of early reports revealed that selective Markovnikov addition, often simply termed "normal" addition, is not always observed with HBr unless air is excluded, leading to the rediscovery of a reproducible and scalable initiator-free protocol.
- Galli, Marzia,Fletcher, Catherine J.,Del Pozo, Marc,Goldup, Stephen M.
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supporting information
p. 5622 - 5626
(2016/07/06)
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- Construction of chiral 2-substituted octahydroindoles from cyclic ketones and nitroolefins bearing only one α-substituent
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A dual catalytic system has been developed following the screening of a series of chiral primary amine catalysts and chiral phosphoric acid catalysts for the Michael addition of cyclic ketones to nitroolefins bearing only one α-substituent. The resulting γ-nitro ketones, which contain a substituent on the carbon connected to the nitro group, were formed in excellent yields (>80%) with high levels of stereoselectivity (up to 94:6 dr and 98% ee) when the reaction was performed in benzene at 0 °C with 10 mol% of the optimal amine/phosphoric acid combination (1:1) as a catalyst. Subsequent reduction of the nitro group followed by intramolecular reductive amination could afford optically active cis-octahydroindole analogues bearing a non-functional substituent at their 2-position.
- Han, Yong,Zheng, Bo,Peng, Yungui
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supporting information
p. 1136 - 1142
(2015/04/22)
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- A novel method to access chiral nonnatural 2,4-disubstituted pyrrolidines from aldehydes and nitroolefins only with an α-substituent
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A series of α-substituted nitroolefins were employed in organocatalytic asymmetric Michael reactions with aldehydes. γ-Nitro carbonyl products were achieved in good yields (up to 86%) with good stereoselectivities (up to 96% ee and 24 : 1 dr). Reduction of the nitro group followed by intramolecular reductive amination successfully afforded various novel optically active 2,4-disubstituted pyrrolidine compounds.
- Zheng, Bo,Wang, Hui,Han, Yong,Liu, Changlu,Peng, Yungui
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supporting information
p. 4561 - 4563
(2013/06/04)
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- Palladium-catalyzed decarboxylative cross-coupling reaction between heteroaromatic Carboxylic acids and Aryl halides
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"Chemical Equation Presented" A full overview of the decarboxylative cross-coupling reaction between heteroaromatic carboxylic acids and aryl halides is described. This transformation employs palladium catalysts with short reaction times providing facile synthesis of aryl-substituted heteroaromatics. The effect of each reaction parameter including solvent, base, and additive employed as well as the full substrate scope of this transformation are reported. Mechanistic evidence is also disclosed that sheds light on possible reaction pathways.
- Bilodeau, Francois,Brochu, Marie-Christine,Guimond, Nicolas,Thesen, Kris H.,Forgione, Pat
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experimental part
p. 1550 - 1560
(2010/06/12)
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- Stereoselective alcohol silylation by dehydrogenative Si-O coupling: Scope, limitations, and mechanism of the Cu-H-catalyzed non-enzymatic kinetic resolution with silicon-stereogenic silanes
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Ligand-stabilized copper(I)hydride catalyzes the dehydrogenative Si-O coupling of alcohols and silanes-a process that was found to proceed without racemization at the silicon atom if asymmetrically substituted. The present investigation starts from this pivotal observation since silicon-stereogenic silanes are thereby suitable for the reagent-controlled kinetic resolution of racemic alcohols, in which asymmetry at the silicon atom enables discrimination of enantiomeric alcohols. In this full account, we summarizeour efforts to systematically examine this unusual strategy of diastereoselective alcohol silylation. Ligand (sufficient reactivity with moderately electron-rich monophosphines), silane (reasonable diastereocontrol with cyclic silanes having a distinct substitution pattern) as well as substrate identification (chelating donor as a requirement) areintroductorily described. With these basic data at hand, the substrate scope was defined employing enantiomerically enriched tert-butyl-substituted 1-silatetraline and highly reactive 1-si-laindane. The synthetic part is complemented by the determination of the stereochemical course at the silicon atom in the Si-O coupling step followed by its quantum-chemical analysis thus providing a solid mechanistic picture of this remarkable transformation.
- Rendler, Sebastian,Plefka, Oliver,Karatas, Betuel,Auer, Gertrud,Froehlich, Roland,Mueck-Lichtenfeld, Christian,Grimme, Stefan,Oestreich, Martin
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supporting information; scheme or table
p. 11512 - 11528
(2009/12/07)
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- Synthesis, radiosynthesis and preliminary in vivo evaluation of [ 123I]-(4-fluorophenyl) {1-[2-(2-iodophenyl)ethyl]piperidin-4-yl} methanone, a potential 5-HT2A-antagonist for SPECT brain imaging
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Many people suffer from psychiatric illnesses like depression and anorexia. Relevant to these diseases is amongst others a malfunctioning of brain 5-HT2A-receptors. To allow in vivo quantification of these receptors with Single Photon Emission
- Blanckaert,Vandecapelle,Staelens,Burvenich,Dierckx,Slegers
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p. 591 - 598
(2007/10/03)
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- Urokinase inhibitors
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Compounds having the formula are inhibitors of urokinase and are useful in the treatment of diseases in which urokinase plays a role. Also disclosed are urokinase-inhibiting compositions and a method of inhibiting urokinase in a mammal.
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- Ukokinase inhibitors
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Compounds having the formula are inhibitors of urokinase and are useful in the treatment of diseases in which urokinase plays a role. Also disclosed are urokinase-inhibiting compositions and a method of inhibiting urokinase in a mammal.
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- Sequential hydrostannylation-cyclisation of δ- and ω-allenyl aryl halides. Cyclisation at the proximal carbon
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Palladium catalysed hydrostannylation of (Bu3SnH, THF, O°C) of δ- and ω-allenyl aryl halides followed by mono- or bis-cyclisation (MeCN, 80°C) affords small (5-7), large (11-17) and spirocyclic rings in which cyclisation occurs at the proximal
- Grigg, Ronald,Sansano, Jose M.
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p. 13441 - 13454
(2007/10/03)
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- Synthesis of Biological Markers in Fossil Fuels. 2. Synthesis and 13C NMR Studies of Substituted Indans and Tetralins
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Unambiguous syntheses of all possible methyl, ethyl, n-propyl, and n-butyl derivatives of indan and tetralin were developed using the Kumada coupling procedure involving the reaction of aryl or vinyl halides with Grignard reagents in the presence of nickel(II) chloride.An analysis of the 13C NMR spectra of these compounds was also completed.
- Adamczyk, Maciej,Watt, David S.,Netzel, Daniel A.
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p. 4226 - 4237
(2007/10/02)
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- Six-membered-ring annulation via a conjugate addition/alkylation sequence using functionalized aryllithium reagents and vinyl sulfones
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A new method, which is a one-flask procedure involving addition of substituted aryllithium reagents 6 to vinyl sulfones 8 and 9 followed by spontaneous intramolecular alkylation of the resulting α-lithio sulfones, has been developed for the annulation of tetrahydronaphtalene moieties onto preexisting carbon frameworks.The aryllithium reagents employed in this study are the previously investigated intermediates obtained by the chemoselective lithium-halogen exchange reactions of simple as well as oxygenated o-halo-β-phenethyl halides 5.The annulation products 11 and 12 may be subjected to various further transformations which should makethe overall sequences of considerable utility in the synthesis of steroids and other polycyclic systems.
- Ponton, John,Helquist, Paul,Conrad, Preston C.,Fuchs, Philip L.
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p. 118 - 122
(2007/10/02)
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- 1,2-Dihydro-2-imino-1-(bromophenylalkyl)pyrimidines
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Compounds of the formula SPC1 Exhibit central nervous system stimulating properties and act as muscle relaxants.
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