3825-64-7Relevant academic research and scientific papers
Zirconocene-mediated and/or catalyzed unprecedented coupling reactions of alkoxymethyl-substituted styrene derivatives
Ikeuchi, Yutaka,Taguchi, Takeo,Hanzawa, Yuji
, p. 4354 - 4359 (2007/10/03)
Reactions of o-(alkoxymethyl)styrene derivatives with a stoichiometric amount of zirconocenebutene complex (zirconocene equivalent, "Cp 2Zr") brought about an insertion of the zirconocene species into a benzylic carbon-oxygen bond. The oxidative insertion of Cp2Zr to the benzylic carbon-oxygen bond is a result of sequential reactions: (i) formation of zirconacyclopropane by the ligand exchange with o-(alkoxymethyl)styrene, (ii) elimination of the alkoxy group 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 gave rise to the analogous tetracyclic compounds regardless of the amount of "Cp2Zr" (stoichiometric or catalytic). Heterocoupling product between o-(1-alkoxyisopropyl)styrene and styrene congeners was obtained in high cis stereo- and regioselectivity by treating o-(1-alkoxyisopropyl)styrene derivatives with "Cp2Zr" in the presence of an excess amount of styrene derivatives.
