Copper-Catalyzed Allylations of Zirconocene Intermediates Generated from o-Alkenyl or o-Alkynylbenzyl Ether Derivatives and Zirconocene−Butene Complex
摘要:
o-Alkenyl or alkynyl benzylzirconocene intermediate, which was readily generated by the reaction of 2-alkoxymethyl-styrene or 2-alkoxymethyl-1-(trimethylsilylethynyl)-benzene derivative with zirconocene-butene complex (Negishi reagent, "Cp2Zr"), reacted with allyl or propargyl halides in the presence of a catalytic amount of CuCl to give allylation or allenylation products. Conversion to Dane's diene, which is a key intermediate for estrone synthesis, was efficiently carried out by enyne olefin metathesis of the allylation products.
repetitive use of Cp(2)ZrBu(2) (Negishi reagent) was applied in the synthesis of three 3-methoxyestra-1,3,5(10)-trienone isomers within four steps from the advanced intermediate 11. The overall synthesis is based on three zirconium-mediated reactions: (a) oxidative addition of a benzyl ether, (b) cyclization of an allyl-ene compound, and (c) cyclocarbonylation of a diene. The presented synthesis demonstrates
Copper-Catalyzed Allylations of Zirconocene Intermediates Generated from <i>o</i>-Alkenyl or <i>o</i>-Alkynylbenzyl Ether Derivatives and Zirconocene−Butene Complex
作者:Yutaka Ikeuchi、Takeo Taguchi、Yuji Hanzawa
DOI:10.1021/jo048860b
日期:2005.1.1
o-Alkenyl or alkynyl benzylzirconocene intermediate, which was readily generated by the reaction of 2-alkoxymethyl-styrene or 2-alkoxymethyl-1-(trimethylsilylethynyl)-benzene derivative with zirconocene-butene complex (Negishi reagent, "Cp2Zr"), reacted with allyl or propargyl halides in the presence of a catalytic amount of CuCl to give allylation or allenylation products. Conversion to Dane's diene, which is a key intermediate for estrone synthesis, was efficiently carried out by enyne olefin metathesis of the allylation products.
Zirconocene-Mediated and/or Catalyzed Unprecedented Coupling Reactions of Alkoxymethyl-Substituted Styrene Derivatives
作者:Yutaka Ikeuchi、Takeo Taguchi、Yuji Hanzawa
DOI:10.1021/jo0502293
日期:2005.5.1
through an aromatic conjugate system giving metalated o-quinodimethane species, and (iii) transfer of zirconium metal to the benzylic position. Through use of a catalytic amount of “Cp2Zr”, however, unprecedented homo-coupling reactions (dimerization) of o-(alkoxymethyl)styrene derivatives occurred to give a tetracyclic compound. On the other hand, reactions of o-(1-alkoxyisopropyl)styrene derivatives