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Use of WO(4)(2-) on layered double hydroxides for mild oxidative bromination and bromide-assisted epoxidation with H(2)O(2).
Sels, B F; De Vos, D E; Jacobs, P A.
Afiliação
  • Sels BF; Centrum voor Oppervlaktechemie en Katalyse, Katholieke Universiteit Leuven, Kardinaal Mercierlaan 92, 3001 Heverlee, Belgium.
J Am Chem Soc ; 123(34): 8350-9, 2001 Aug 29.
Article em En | MEDLINE | ID: mdl-11516284
Tungstate, exchanged on a (Ni,Al) layered double hydroxide, is applied as a heterogeneous catalyst in the oxidation of bromide with H(2)O(2) and the ensuing electrophilic bromination of olefins. The high halogenation activity of the catalyst in essentially neutral conditions mimicks the activity of V-bromoperoxidase enzymes. In water, aromatic and aliphatic olefins are selectively converted to bromohydrins; in methanol, methoxybromides are produced. In appropriate solvent conditions, the bromohydroxylation of geminally di-, tri-, and tetrasubstituted olefins proceeds via dehydrobromination to the epoxide. Evidence for this mechanism is provided by kinetic and labeling experiments. This one-pot alternative for the two-step halohydrin epoxidation process is enabled by the mild pH conditions; bromide is effective in substoichiometric, catalytic amounts. All new catalytic procedures are characterized by a high oxidative stability of the catalyst, high productivity of the catalyst on weight basis, high W turnover frequencies in ambient conditions (up to 50 mol of product per W per h), and high chemo-, regio-, and stereoselectivities.
Assuntos
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Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Brometos / Compostos de Tungstênio / Alcenos / Hidrocarbonetos Bromados / Peróxido de Hidrogênio Idioma: En Revista: J Am Chem Soc Ano de publicação: 2001 Tipo de documento: Article País de afiliação: Bélgica
Buscar no Google
Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Brometos / Compostos de Tungstênio / Alcenos / Hidrocarbonetos Bromados / Peróxido de Hidrogênio Idioma: En Revista: J Am Chem Soc Ano de publicação: 2001 Tipo de documento: Article País de afiliação: Bélgica