- New reactivity of functionalised organolithium compounds in the presence of Cu(I) or Cu(II) salts: Conjugate addition, acylation or dimerisation
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The reaction of functionalised organolithium compounds 1 with electrophilic olefins 2 in the presence of copper(I) iodide and HMPA in THF at -78°C leads, after hydrolysis with a saturated solution of ammonium chloride, to the corresponding products 3 resulting from a conjugate addition. The same process but using an acyl chloride instead of the electrophilic olefins affords the expected ketone 4 from an acylation process. Finally, when intermediates 1 are treated with copper(II) chloride in THF at -78°C, the corresponding dimers 5 are isolated after the same hydrolytic treatment.
- Pastor, Isidro M,Yus, Miguel
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- Preparation and coordinating properties of {CH2(o-C 6H4CH2SbMe2)}2, a novel wide-angle cis-chelating distibine
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The unique wide-angle distibine, {CH2(o-C6H 4CH2SbMe2)}2, 1, has been prepared indirectly by reaction of Me2SbCl with the di-Grignard formed unexpectedly by coupling of o-C6H4(CH2MgCl) 2 in concentrated thf solution, and directly by treatment of the {CH2(o-C6H4CH2MgCl)}2 with Me2SbCl. The very oxygen-sensitive distibine 1 has been characterised by 1H and 13C{1H} NMR spectroscopy and high-resolution EIMS. Oxidation of 1 with Br2 gives the air-stable tetrabromide {CH2(o-C6H4CH 2SbMe2Br2)}2. Surprisingly, 1 shows a very strong tendency to function as a cis-chelate, e.g. to Pt(iv) in the complex [PtMe3I(1)], forming an 11-membered ring and providing a stable Pt(iv) stibine complex, the crystal structure of which shows the Sb-Pt-Sb angle to be 95.96(1)°. The yellow Pt(ii) complex [PtCl2(1)] is obtained from reaction of [PtCl2(MeCN)2] with 1 and IR spectroscopic data and a crystal structure determination confirm the Cl ligands are mutually cis in this species. Reaction of [W(CO)4(piperidine) 2] with 1 in refluxing EtOH gives [W(CO)4(1)], the IR spectrum of which shows four ν(CO) bands, also consistent with cis-Sb 2 coordination. The cis-chelation is also confirmed by single-crystal X-ray structure determinations of two polymorphs of [W(CO)4(1)]. The Royal Society of Chemistry 2006.
- Brown, Michael D.,Levason, William,Reid, Gillian,Webster, Michael
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p. 5648 - 5654
(2008/02/10)
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- Copper(I) or (II)-mediated conjugate addition or dimerisation of functionalised organolithium compounds
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The reaction of different functionalised organolithium intermediates 1- 3 with several electrophilic olefins 6 (2-cyclopentenone, 2-cyclohexenone, methyl vinyl ketone, benzylideneacetone, benzylideneacetophenone and ethyl acrylate) in the presence of copper(I) salts (bromide and iodide) in THF at -78°C gives, after hydrolysis with ammonium chloride, the expected products resulting from a conjugate addition. In the presence of copper(II) chloride intermediates 1-5 undergo dimerisation to yield the expected dimers. (C) 2000 Elsevier Science Ltd.
- Pastor, Isidro M.,Yus, Miguel
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p. 1589 - 1592
(2007/10/03)
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- Efficient radical coupling of organobromides using dimanganese decacarbonyl
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Wurtz-type radical coupling of a variety of allylic and benzylic bromides was observed on irradiation with dimanganese decacarbonyl in excellent yield (77-99%). Efficient cross-coupling of two different bromides was also readily achieved.
- Gilbert, Bruce C.,Lindsay, Chris I.,McGrail, P. Terry,Parsons, Andrew F.,Whittaker, David T.E.
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p. 2711 - 2718
(2007/10/03)
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- Selective Preparation of Polycyclic Aromatic Hydrocarbons. Part 7. A Preparative Route to 10,11-Dihydro-5H-dibenzo-cycloheptenes Using Friedel-Crafts Intramolecular Cyclobenzylation
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Cyclobenzylation of 2-hydroxymethyldiphenylethanes 4 and 2,2'-bis(hydroxymethyl)diphenylethanes 13 in the presence of a solid perfluorinated sulfonic acid resin, Nafion-H, as a catalyst results in novel polycyclic aromatic hydrocarbons, dibenzocyclopentenes.Dibenzocyclopentenes were also prepared from diphenylethanes by a benzylation reaction, which incorporates chloromethylation of a hydrocarbon followed by Friedel-Crafts intramolecular cyclization reaction.The present method involving the action of ClCH2OMe and TiCl4 on a variety of diphenylethanes (constructed such that electrophilic substitution occurs ortho to the diphenylethane linkage) offers a convenient, mild one-pot synthesis of substituted dibenzocycloheptenes.The mechanism of these reactions is also discussed.
- Yamato, Takehiko,Sakaue, Naozumi,Komine, Masayasu,Nagano, Yoshiaki
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p. 1708 - 1735
(2007/10/03)
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- Electron-transfer-induced reductive cleavage of phthalans: Reactivity and synthetic applications
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The behavior of phthalan (1a) was investigated under conditions of electron transfer from alkali metals in aprotic solvents. Reaction with lithium in the presence of a catalytic amount of naphthalene in THF led to the reductive cleavage of an arylmethyl carbon-oxygen bond, with formation of a stable dilithium compound. Trapping of this intermediate with several electrophiles (alkyl halides, carbonyl derivatives, CO2) was successful. The extension of this procedure to several substituted phthalans (1b-i) was investigated, and the regiochemistry as well as the synthetic usefulness of these reactions are discussed.
- Azzena, Ugo,Demartis, Salvatore,Melloni, Giovanni
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p. 4913 - 4919
(2007/10/03)
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