- Enantioselective synthesis of tertiary and quaternary stereogenic centers: Copper/phosphoramidite-catalyzed allylic alkylation with organolithium reagents
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An efficient and highly enantioselective copper-catalyzed allylic alkylation of disubstituted allyl halides with primary and secondary organolithium reagents using phosphoramidite ligands is reported. The use of trisubstituted allyl bromides allows, for the first time, the enantioselective synthesis of all-carbon quaternary stereogenic centers with these reactive organometallic reagents.
- Fananas-Mastral, Martin,Perez, Manuel,Bos, Pieter H.,Rudolph, Alena,Harutyunyan, Syuzanna R.,Feringa, Ben L.
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supporting information; experimental part
p. 1922 - 1925
(2012/04/17)
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- Grignard allylic substitution catalyzed by imidazol-2-ylidene- and imidazol-4-ylidene-magnesium complexes
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In the presence of a catalytic amount of 1,2-disubstituted or 1,2,3-trisubstituted imidazolium salts, γ-substituted allyl chlorides reacted with alkyl Grignard reagents to undergo substitution reactions in an SN2′-selective fashion, where the magnesium ate complexes [(N-heterocyclic carbene-MgR3)-(MgX)+] of imidazol-2-ylidenes or imidazol-4-ylidenes, generated in situ, were postulated as the active species. It was observed that the reactions with imidazol-4-ylidene catalysts were faster than those with imidazol-2-ylidenes. Enantioselective catalysis using a chiral imidazolium salt was preliminarily investigated.
- Okamoto, Sentaro,Ishikawa, Hiroyuki,Shibata, Yoshimi,Suhara, Yu-Ichiro
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supporting information; experimental part
p. 5704 - 5707
(2010/11/16)
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- Cobalt-catalyzed regioselective dehydrohalogenation of alkyl halides with dimethylphenylsilylmethylmagnesium chloride
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Cobalt-catalyzed reactions of haloalkanes with dimethylphenylsilylmethylmagnesium chloride result in highly regioselective dehydrohalogenation. The reaction does not follow the conventional E2 elimination mechanism but includes β-hydride elimination from the corresponding alkylcobalt intermediate. The interesting reaction mechanism of the cobalt-catalyzed dehydrohalogenation offered unique transformations that are otherwise difficult to attain. Copyright
- Kobayashi, Tsuneyuki,Ohmiya, Hirohisa,Yorimitsu, Hideki,Oshima, Koichiro
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body text
p. 11276 - 11277
(2009/02/05)
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- The Synthesis of α-Stannyl Silanes and Their Use in the Formation of Alkenes
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α-Stannyl-silanes were prepared from aldehydes via α-hydroxy- and α-chloro-silanes.Stannyl-silane 5d was transmetallated using n-butyllithium and the resultant α-lithio-silane condensed with aldehydes to yield alkenes.
- Barrett, Anthony G. M.,Hill, Jason M.
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p. 3285 - 3288
(2007/10/02)
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