- SELECTIVITY IN ALLYLIC SUBSTITUTIONS WITH ORGANOMETALLICS THROUGH NEIGHBOURING COORDINATION. SYNTHESIS AND REACTIONS OF COPPER(I) ?-COMPLEXES WITH 2-ALLYLLOXYBENZOTHIAZOLES
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2-Allylloxybenzothiazoles react with CuBr to give stable CuI ?-complexes.These complexes undergo nucleophilic attack by organomagnesium compounds to give olefins with very high regio- and stereo-specificity.
- Calo, Vincenzo,Lopez, Luigi,Pesce, Giannangelo
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- A General Approach to Intermolecular Olefin Hydroacylation through Light-Induced HAT Initiation: An Efficient Synthesis of Long-Chain Aliphatic Ketones and Functionalized Fatty Acids
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Herein, an operationally simple, environmentally benign and effective method for intermolecular radical hydroacylation of unactivated substrates by employing photo-induced hydrogen atom transfer (HAT) initiation is described. The use of commercially available and inexpensive photoinitiators (Ph2CO and NHPI) makes the process attractive. The olefin hydroacylation protocol applies to a wide array of substrates bearing numerous functional groups and many complex structural units. The reaction proves to be scalable (up to 5 g). Different functionalized fatty acids, petrochemicals and naturally occurring alkanes can be synthesized with this protocol. A radical chain mechanism is implicated in the process.
- Guin, Joyram,Paul, Subhasis
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supporting information
p. 4412 - 4419
(2021/02/05)
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- Highly enantioselective Cu-catalysed allylic substitutions with Grignard reagents
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A catalyst system able to perform highly enantioselective Cu-catalysed allylic alkylations with Grignard reagents is described. The Royal Society of Chemistry 2006.
- Lopez, Fernando,Van Zijl, Anthoni W.,Minnaard, Adriaan J.,Feringa, Ben L.
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p. 409 - 411
(2008/02/05)
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- Zirconium porphyrins as novel active catalysts for highly regio- And stereoselective ethylalumination of alkynes
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Zirconium(IV) complexes of 5, 10, 15, 20-tetraphenylporphyrin ((TPP)ZrX2) catalyze highly regioand stereo-selective ethylalumination of terminal alkynes with satisfactorily high turnover numbers.
- Shibata, Kenji,Aida, Takuzo,Inoue, Shohei
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p. 1077 - 1080
(2007/10/02)
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- THE HYDRIDOPENTACYANOCOBALTATE ANION INDUCED DEOXYGENATION OF ALLYLIC ALCOHOLS USING β-CYCLODEXTRIN AS A PHASE TRANSFER AGENT
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β-Cyclodextrin promotes the deoxygenation of allylic alcohols to olefins using hydrogen and the in situ generated hydridopentacyanocobaltate anion.Internal olefins, of trans-stereochemistry, are the principal reaction products (i. e., no cis-products are formed).
- Lee, Jong-Tae,Alper, Howard
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p. 4101 - 4104
(2007/10/02)
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- CROSS-COUPLIN REACTIONS BETWEEN SOME ALLYL, HOMOALLYL, AND HOMOPROPARGYL SUBSTRATES AND TRIALKYLALANES OR DIALKYL- AND DIARYL-MAGNESIUM DERIVATIVES
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Trialkylalanes and dilkyl- and diaryl-magnesium derivatives can be cross-coupled with allyl ethers and esters, sulphides, and quaternized allylamines.The reactions proceed uncatalyzed either with mild conditions or in the presence of copper complex catalysts to result in high yields of mono- and di-olefins of various structures.The alkylation of homoallyl or homopropargyl tosylates by trialkylalanes is accompanied by cyclization, which leads to alkyl-substituted cyclopropanes. i.e. cyclobutanes and cyclopropylidenes.
- Tolstikov, G. A.,Dzhemilev, U. M.
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p. 133 - 144
(2007/10/02)
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- Syntheses a l'aide de sulfones. XVIII. Utilisation des disulfones-1,1 pour la synthese stereoselective de composes olefiniques
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2-Alkenyl-1,1-disulfones 4 are readily available in excellent yields by condensation of aldehydes with bisaryl or bisalkylsulfonylmethanes in the presence of piperidine acetate and molecular sieves at room temperature.A small amount of the 1-alkenyl isomer is also found when the aldehyde is α-substituted but it can be converted into the 2-alkenyl isomer by base catalysed equilibration.The 2-alkenyl-1,1-disulfones display only E geometry whereas E allylic monosulfones are difficult to isolate in a state of stereochemical purity (about 20percent of the Z isomer at equilibrium (8)).Alkylation is readily performed: treatment of 4 and 6 by sodium hydride in dimethylformamide and then by methyl iodide gives disulfones 5 E and 7 in 78-95percent yields.The alkylation of 4 (R=Et) by butyl iodide gives 70percent of 5 E(R=Et, R'=n-Bu) resulting from alkylation at the α position and 8percent of 3 (R=Et, R'=n-Bu) resulting from alkylation at the γ position.The α isomer is readily purified by crystallization.Reduction of disulfones 4 or 5 by aluminium amalgam leads quantitatively to allylic sulfones 2E or 8E.Olefins 9E are obtained upon total reduction of disulfones 4 or 5 by lithium in ethylamine at -78 deg C but in the case of disulfones 5 the olefins 9E are contaminated by isomers 10E and 10Z.
- Cuvigny, Therese,Penhoat, Catherine Herve Du,Julia, Marc
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- Selectivity in the Allylic Substitutions with Organometallics through Neighboring Coordination. 2-(Allyloxy)benzothiazoles as SN2' Electrophiles for Regio- and Stereoselective Olefin Syntheses
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An efficient control of the regio- and stereochemistry in the allylic substitutions with organomagnesium compounds has been achieved by using 2-(allyloxy)benzothiazoles as substrates in the presence of copper bromide.The selectivity is due to the coordinative effects of the substrates toward the organometallic species.
- Calo, Vincenzo,Lopez, Luigi,Pesce, Giannangelo,Calianno, Antonia
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p. 4482 - 4485
(2007/10/02)
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- The effect of steric size of leaving group on rates of the competing syn- and anti-pathways in bimolecular elimations
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Approximate rates of the competing syn- and anti-pathways have been determined in t-C4H9OK-t-C4H9OH promoted elimination from two homologous series of tosylates: I-OTs -> trans-III ( R=H, CH3, C2H5, n-C3H7, i-C3H7, t-C4H9) and II-OTs -> trans-IV ( R=CH3, C2H5, n-C3H7, i-C3H7, t-C4H9).A comparison has been made with rates of the same processes in the elimination of the corresponding trimethylammonium salts: I-N(+)(CH3)3 -> trans-III and II-N(+)(CH3)3 -> trans IV.The title effect is demonstrated by a comparative analysis of the rate patterns obtained for the two leaving groups.
- Zavada, Jiri,Pankova, Magdalena
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p. 2171 - 2178
(2007/10/02)
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- THE EFFECT OF CROWN ETHER ON STERIC HINDRANCE TO BASE APPROACH IN BIMOLECULAR ELIMINATION: EVIDENCE AGAINST CLUMP AGGREGATE MODEL OF ION-PAIRED ALKOXIDE BASE
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The effect of 18-crown-6-ether upon geometrical orientation and rates was investigated in tert-C4H9OK-tert-C4H9OH promoted anti-elimination from two homologous series of tosylates, RCH2CHOTsC5H11 and RCHOTsCH2C5H11 (R = H, CH3, C2H5, n-C3H5, iso-C3H7, tert-C4H9).Steric requirements of the cis- and trans-stereoselective base species operating in the reaction in the absence and in the presence of the crown ether, respectively, have been assessed.An unambiguous distinction has been made between two pending models of the cis-stereoselective (ion-paired) base.
- Pankova, Magdalena,Zavada, Jiri
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p. 3150 - 3159
(2007/10/02)
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- Mercapto phenolic and alkylthio phenolic antioxidants
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2-Mercapto phenol and/or 4-mercapto phenol are reacted with a compound selected from olefins, alcohols, and organic halides for example, styrene and isobutylene, to form (hydrocarbyl) thio phenolic antioxidants such as 2,6-di-tert. butyl-4-(tert.butylthio) phenol and 2,6-di(α-phenylethyl)-4-(α-phenylethylthio)phenol.
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