- Preparation of Thioanisole Biscarbanion and C-H Lithiation/Annulation Reactions for the Access of Five-Membered Heterocycles
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The synthesis, isolation, and X-ray structure of a thioanisole-based trilithium complex are reported. On the basis of the double-lithiation strategy, two novel synthetic methodologies have been developed under mild reaction conditions (room temperature): (1) reactions of lithiated thioanisoles with nitriles give benzoisothiazoles via a [3 + 2]-type of approach with two new bond formations and (2) formation of benzothiophenes from thioanisoles and amides through a [4 + 1] pattern forming 4 new chemical bonds.
- Zhu, Ranran,Liu, Zheyuan,Chen, Jie,Xiong, Xiaoyu,Wang, Yuntao,Huang, Lin,Bai, Jinshan,Dang, Yanfeng,Huang, Jianhui
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supporting information
p. 3161 - 3165
(2018/06/11)
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- Evolution of a Polyene Cyclization Cascade for the Total Synthesis of (?)-Cyclosmenospongine
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We report a full account on the development of a unique cationic polyene cyclization for the total synthesis of the tetracyclic meroterpenoid (?)-cyclosmenospongine. A highly convergent three-component coupling strategy enabled rapid access to individual cyclization precursors that were tested for their reactivity. The successful transformation generates three rings and sets four consecutive stereocenters in a single operation proceeding in a highly efficient manner to give exclusively the trans-decalin framework. In addition, we found that the enol ether geometry and the relative configuration of C3 and C8 are crucial for the success of the polyene cyclization.
- Speck, Klaus,Magauer, Thomas
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supporting information
p. 1157 - 1165
(2017/02/05)
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- Exploring chromium(III)-alkyl bond homolysis with CpCr[(ArNCMe) 2CH](R) complexes
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A range of paramagnetic Cr(III) monohydrocarbyl complexes CpCr[(ArNCMe)2CH](R) (Ar = ortho-disubstituted aryl; R = primary alkyl, trimethylsilylmethyl, benzyl, phenyl, alkenyl, or alkynyl) were synthesized to investigate how varying the steric and electronic properties of the R group affected their propensity for Cr-R bond homolysis. Most complexes were prepared by salt metathesis of known CpCr[(ArNCMe)2CH](Cl) compounds in Et2O with commercial RMgCl solutions, although more sterically demanding combinations of Ar and R groups necessitated the use of halide-free MgR2 reagents and the Cr(III) tosylate or triflate derivatives. Alternative synthetic routes to Cr(III)-R species using the previously reported Cr(II) compounds CpCr[(ArNCMe)2CH] and sources of R? radicals (e.g., BEt3 and air) were also explored. The UV-vis spectra of the CpCr[(ArNCMe)2CH](R) complexes possessed two strong bands with maximum absorbances in the ranges 395-436 nm and 535-582 nm, with the band in the latter range being particularly characteristic of the Cr(III)-R compounds. The Cr-CH2R bond lengths as determined by single-crystal X-ray diffraction were longer than those in the corresponding Cr-CH3 complexes, typically falling in the range 2.10 to 2.13 A. The Cr(III) benzyl compounds displayed longer Cr-CH2Ph distances, while the bond lengths for the alkenyl and alkynyl species were substantially shorter. The rate of Cr-R bond homolysis at room temperature was determined by monitoring the reaction of Cr(III) neopentyl, benzyl, and isobutyl complexes with excess PhSSPh using UV-vis spectroscopy. Although the other primary alkyl, phenyl, and alkenyl compounds did not undergo appreciable homolysis under these conditions, they were cleanly converted to CpCr[(ArNCMe)2CH](SPh) by photolysis.
- MacLeod, K. Cory,Conway, Julia L.,Patrick, Brian O.,Smith, Kevin M.
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scheme or table
p. 17325 - 17334
(2011/03/01)
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- Organylthio(silyl)carbenes
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The title carbenes 5 can be generated either from diazo compounds 9 by copper-catalyze d catalysis or from chloro(organylthio)methylsilanes 12 by base-induced α-elimination, This is confirmed, by [2+1] cycloadditions with alkenes to give the cyclopropanes
- Wagner, Tobias,Lange, Jens,Grote, Dirk,Sander, Wolfram,Schaumann, Ernst,Adiwidjaja, Gunadi,Adam, Arnold,Kopf, Juergen
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experimental part
p. 5198 - 5207
(2010/01/11)
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- Reaction of trimethylsilanes with Arenes and Alk-1-enes in the Presence of Lewis Acid: Syntheses of - and (1-Arylthioalk-3-enyl)-trimethylsilanes
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Treatment of equimolar amounts of the trimethylsilanes (2) or (3) and electron-rich arenes with an equimolar amount of Lewis acid (SnCl4 or TiCl4) gave the Friedel-Crafts reaction products, trimethylsilanes (4) or (5), in high yields.Similar treatment of the chlorides (2) or (3) with alk-1-enes gave ene type products, trimethylsilanes (12) or (13), in moderate yields.Some chemical transformations of these products are also described.
- Ishibashi, Hiroyuki,Nakatani, Hiroshi,Umei, Yoshizumi,Yamamoto, Wako,Ikeda, Masazumi
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p. 589 - 594
(2007/10/02)
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- EFFICIENT SYNTHETIC METHODOLOGY FOR 1-(PHENYLTHIO)CYCLOPROPYLSILANES, PRECURSORS OF 1-(LITHIO)CYCLOPROPYLSILANES
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Two one flask connective methods for preparing 1-(phenylthio)-cyclopropylsilanes, precursors of 1-(lithio)cyclopropylsilanes, are described.
- Cohen, Theodore,Sherbine, James P.,Mendelson, Stephen A.,Myers, Michael
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p. 2965 - 2968
(2007/10/02)
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- Preparation of Vinylic Sulphones by Peterson Olefination using Phenyl Trimethylsilylmethyl Sulphone
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The anion generated from phenyl trimethylsilylmethyl sulphone using butyl-lithium in dimethoxyethane, readily reacts at -78 deg C with various carbonyl compounds to afford vinylic sulphones on work-up at room temperature.The reaction conditions are tolera
- Craig, Donald,Ley, Steven V.,Simpkins, Nigel S.,Whitham, Gordon H.,Prior, Michael J.
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p. 1949 - 1952
(2007/10/02)
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- Synthesis of Aldehydes from Phenylthiotrimethylsilylmethane
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Phenylthiotrimethylsilylmethyl-lithium (4) reacts with alkyl halides to give 1-phenylthio-1-trimethylsilylalkanes (5), which can also be prepared by the addition of alkyl-lithium to 1-phenylthio-1-trimethylsilylethene (8), or from bis(phenylthio)acetals (11).The 1-phenylthio-1-trimethylsilylalkanes (5) can be converted into the corresponding aldehyde (15) by oxidation to the sulphoxide (13), thermal rearrangement, and hydrolysis of the resultant O-silyl thioacetal (14).
- Ager, David J.
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p. 1131 - 1136
(2007/10/02)
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- The Formation of Allyl Sulphides by Phenylthio-migration: Control by Silicon
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When γ-silyl-β-phenylthio-alcohols are treated with acid, the strategically placed silyl group encourages the rearrangement of the phenylthio-group, both from a secondary migration origin to a secondary migration terminus, and from a secondary migration origin to a tertiary migration terminus (4)->(6).Geraniol/nerol (12) and linalool (14) have been synthesised from a common intermediate (11) using this type of reaction.Phenylthio-migration from a tertiary migration origin (17)->(3) can be controlled to a limited extent by a suitably placed silyl group, but it is easier to achieve direct β-elimination of the silyl and phenylthio-groups (17)->(18).
- Fleming, Ian,Paterson, Ian,Pearce, Andrew
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p. 256 - 262
(2007/10/02)
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- A NEW METHOD FOR PREPARING 1-PHENYLTHIO-1-TRIMETHYLSILYLALKANES: THE PREPARATION OF α-SILYLCARBANIONS AND OLEFINS.
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1-Phenylthio-1-trimethylsilylalkanes(1) are prepared in high yield from 1,1-bis(phenylthio)acetals(2) by reaction with lithium naphthalenide(3) followed by chlorotrimethylsilane. α-Silylcarbanions are formed from the alkanes(1) and lithium naphthalenide(3).Subsequent reaction with carbonyl compounds gave the olefins(4) via the Peterson reaction.
- Ager, David J.
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p. 2923 - 2926
(2007/10/02)
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- A NEW METHOD FOR CONVERTING ALKYL HALIDES TO HOMOLOGOUS ALDEHYDES
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Phenylthiotrimethylsilylmethyl lithium can be alkylated and the product hydrolysed to the aldehydes by oxidation and rearrangement.
- Ager, David J.,Cookson, Richard C.
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p. 1677 - 1680
(2007/10/02)
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