- Br?nsted Acid Catalyzed 1,2-Silyl Shift in Propargyl Silanes: Synthesis of Silyl Dienes and Silyl Indenes
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A general method for generation of allyl carbenium ions from propargyl silanes via a 1,2-silyl shift by Br?nsted acids is reported. Two possible reaction pathways are described. Deprotonation results in silyl dienes with yields from 52% to 92%. Intramolecular Friedel-Crafts reactions of aryl-substituted systems give access to silyl indenes with yields of 18-90% depending on the substitution pattern. The obtained products have been shown to react as alkenyl silanes in Hiyama coupling and electrophilic substitution and as dienes in Diels-Alder cycloaddition.
- Purin?, Mikus,Mishnev, Anatoly,Turks, Maris
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- Ynonylation of Acyl Radicals by Electroinduced Homolysis of 4-Acyl-1,4-dihydropyridines
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Herein we report the conversion of 4-Acyl-1,4-dihydropyridines (DHPs) into ynones under electrochemical conditions. The reaction proceeds via the homolysis of acyl-DHP under electron activation. The resulting acyl radicals react with hypervalent iodine(III) reagents to form the target ynones or ynamides in acceptable yields. This mild reaction condition allows wider functionality tolerance that includes halides, carboxylates, or alkenes. The synthetic utility of this methodology is further demonstrated by the late-stage modification of complex molecules.
- Luo, Xiaosheng,Wang, Ping
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supporting information
p. 4960 - 4965
(2021/07/20)
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- Et2Zn-mediated stoichiometric C(sp)-H silylation of 1-alkynes and chlorosilanes
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A first example of an Et2Zn mediated silylation of 1-aklynes is reported. A series of functional groups are tolerated in this reaction. Mechanistic studies support Zn alkynilides as intermediates in the reaction. This reaction protocol provides a practical method for the preparation of alkynylsilanes and expands the application of organometallic zinc in organic synthesis.
- Huang, Pan,Xu, Dawen,Reich, Robert M.,Kaiser, Felix,Liu, Boping,Kühn, Fritz E.
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supporting information
p. 1574 - 1577
(2019/05/17)
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- Aerobic oxynitration of alkynes with tBuONO and TEMPO
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An efficient method for stereoselective nitroaminoxylation of alkyne has been reported. The reaction enjoys a broad substrate scope, good functional group tolerance, and high yields. Synthetically useful α-nitroketones can be accessed through these products in a single step.
- Dutta, Uttam,Maity, Soham,Kancherla, Rajesh,Maiti, Debabrata
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supporting information
p. 6302 - 6305
(2015/02/19)
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- Facile hydroboration of (Z)-1-trimethylsilyl-1-alkenes with dichloroborane-dioxane complex: An easy access to gem-dimetalloalkanes containing boron and silicon
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(Z)-1-trimethylsilyl-1-alkenes easily prepared by the hydroboration of the corresponding 1-trimethylsilyl-1-alkynes followed by protonolysis with acetic acid, readily react with dichloroborane-dioxane complex in dichloromethane for 6 h. The resulting solution is then treated with 1,3-propane diol in dichloromethane at 0 °C for half an hour to provide the corresponding gem-dimetalloalkanes containing boron and silicon. These α- trimethylsilylalkylboronate esters are purified by vacuum distillation in high yields (72-84%) and the structures of these novel intermediates are further confirmed by selective oxidation with alkaline hydrogen peroxide to provide the corresponding alcohols containing α-trimethylsilyl group in 78-88% isolated yields.
- Bhat, Narayan G.,Villanueva, Mary A.
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p. 1298 - 1300
(2007/10/03)
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- A simple synthesis of B-2-(1-trimethylsilyl-1-alkyl)-1,3,2-dioxaborinanes. Isolation and selective oxidation to 1-trimethylsilyl-1-alkanols
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(Z)-1-Trimethylsilyl-1-alkenes easily prepared by the hydroboration of the corresponding 1-trimethylsilyl-1-alkynes followed by protonolysis with acetic acid, readily react with dibromoborane-methyl sulfide complex in dichloromethane for 6 h. The resulting solution is then treated with 1, 3-propane diol in a 1:1 mixture of dichloromethane and n-pentane at 0°C for half an hour to provide the corresponding gem-dimetalloalkanes containing boron and silicon. These alpha-trimethylsilylalkylboronate esters are purified by vacuum distillation in high yields (72-84%) and the structures of these novel intermediates are further confirmed by selective oxidation with alkaline hydrogen peroxide to provide the corresponding alcohols containing trimethylsilyl group.
- Bhat, Narayan G.,Garza, Amanda
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p. 6833 - 6835
(2007/10/03)
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- A Nickel-catalyzed carbozincation of aryl-substituted alkynes
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The addition of dialkylzincs or diphenylzinc to substituted phenylacetylenes in the presence of catalytic amounts of Ni(acac)2 in THF:NMP mixtures produces syn-carbozincation products with good to excellent regio- and stereoselectivity. After quenching with an electrophile (iodine, acyl chloride, allyl bromide) tetrasubstituted olefines are obtained in good to satisfactory yields. An intramolecular version of the reaction is possible using a terminal triple bond bearing an iodine at a remote position. More substituted iodo-alkynes furnish only reductive elimination products. An application to a stereoselective synthesis of (Z)-tamoxifen (Z:E > 99:1) has been developed.
- Stuedemann, Thomas,Ibrahim-Ouali, Malika,Knochel, Paul
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p. 1299 - 1316
(2007/10/03)
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- New nickel-catalyzed carbozincation of alkynes: A short synthesis of (Z)-tamoxifen
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A new highlight in the repertoire of carbometalation reactions is the highly stereo- and regioselective nickel-catalyzed carbozincation of internal alkynes. This is exemplified by a short and effective synthesis of the anti-breast-cancer drug (Z)-tamoxifen. This reaction also allows the stereoselective synthesis of various tri- and tetrasubstituted olefins in good yield.
- Studemann,Knochel
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- A new route to α,β-unsaturated aldehydes using the condensation of trimethylsilyl β-trimethylsilyl enol ethers with aldehydes
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β-Trimethylsilyl enol ethers 1 (Z) obtained from β-bromoenolethers 2 were condensed with aliphatic and aromatic aldehydes in the presence of a catalytic quantity of trimethylsilyl triflate leading to ethylenic aldehydes 3 (E) with good yields (79-90%).
- Duhamel, Lucette
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p. 7745 - 7748
(2007/10/02)
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- Carbocycle Formation via Intramolecular Insertion of Alkynes into Titanium-Carbon Bonds
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Treatment of alkyl titanocene chloride complexes with the Lewis acids EtAlCl2 or Me2AlCl resulted in intramolecular insertion of a tethered alkyne into the Ti-C bond.Regioselective alkyne insertion produced exocyclic trisubstituted alkene products resulting from four-, five-, and six-membered ring formation.In the case of cyclohexane formation, the alkyne was found to insert with syn stereoselectivity.
- Harms, Arthur E.,Stille, John R.
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p. 6565 - 6568
(2007/10/02)
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- STEREOSELECTIVE SYNTHESIS AND CHARACTERIZATION OF 2-ALKYL AND 2-(HETERO)ARYL SUBSTITUTED (Z)- AND (E)-1-TRIMETHYLSILYL-1-TRIMETHYLSTANNYLETHENES
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The regio- and stereoselective syntheses of the (Z)- and (E)-stereoisomers of some 1-trimethylsilyl-2-(hetero)arylethenylstannanes and 1-trimethylsilyl-2-alkylethenyltrimethylstannanes of general formula (Z)-2, (E)-2, (Z)-3, and (E)-3, respectively, are reported.The strategy followed to prepare (Z)-2, (E)-2, and (E)-3, involves: a) stereoselective cis- and trans-hydroalumination of the corresponding 1-alkynylsilanes; b) conversion of the stereodefined 1-alkenyl-1-silylalanes so obtained into the corresponding aluminates; and c) the cuprous iodide-triethyl phosphite complex mediated reaction of these aluminates with trimethyltin chloride.Compounds (Z)-3, have been prepared by carbocupration of ethynyltrimethylsilane, 12, followed by treatment with trimethyltin chloride.Compounds (Z)-2, (E)-2, (Z)-3, and (E)-3, have been characterized by MS spectrometry and 1H NMR spectroscopy and their configuration has been unambiguously assigned by 119Sn NMR spectroscopy.The results of an attempt to syntesize a 2-alkyl substituted (E)-1-trimethylsilyl-1-trimethylstannyl-2-arylethene are also discussed.
- Rossi, Renzo,Carpita, Adriano,Bellina, Fabio,Santis, Massimo De,Veracini, Carlo Alberto
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p. 457 - 463
(2007/10/02)
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- Simple preparation of α-bromo acyl silanes α-ketoacyl silanes and α-ketoesters from silyl acetylenes
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α-Bromo- and α-keto-acyl silanes may simply and efficiently be prepared in short reaction schemes from silyl acetylenes; α-ketoacyl silanes are also implicated in a one-pot synthesis of α-ketoesters from silyl acetylenes.
- Bulman Page, Philip C.,Rosenthal, Stephen
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p. 2573 - 2586
(2007/10/02)
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- BIS(TRMETHYLSILYL)-1,3 ALCYNES-1 : PREPARATION A PARTIR DE SILANES PROPARGYLIQUES ET APPLICATION A LA SYNTHESE DE SILANES ALLENIQUES α-FONCTIONNELS
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1,3-bis(trimethylsilyl)-1-alkynes may be obtained from trimethylsilylpropargylsilanes by metallation with n-butyllithium following by reaction with trimethylsilylchloride ; these silanes easily react with acetals, in presence of titanium tetrachloride, to produce α-functional allenyltrimethylsilanes.
- Pornet, Jacques,Mesnard, Danielle,Miginiac, Leone
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p. 4083 - 4086
(2007/10/02)
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