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Highly regioselective reaction of zirconocene-alkene complexes with aldehydes or ketones

1994; Elsevier BV; Volume: 473; Issue: 1-2 Linguagem: Inglês

10.1016/0022-328x(94)80112-6

1872-8561

Noriyuki Suzuki, Christophe Rousset, Koichiro Aoyagi, Martin Kotora, Tamotsu Takahashi, Maki Hasegawa, Yu Nitto, Masahiko Saburi,

Radioactive element chemistry and processing

Reactions of zirconocene-alkene complexes Cp2Zr(CH2CHR)(PR′3) (R  H, Me, Et, SiR″3 or Ar) with aldehydes or ketones were investigated. Zirconocene-ethylene, -propylene or 1-butene complexes reacted with aldehydes or ketones at terminal carbons of alkenes to give the corresponding alcohols after hydrolysis with a high regioselectivity. A similar type of reaction product was also obtained by a reaction of zirconacyclopentanes with aldehydes. This reaction proceeded via β-β′carbon-carbon bond cleavage of zirconacyclopentanes. A reaction of zirconocene-vinylsilane complexes with ketones afforded 3-trimethylsilyl-1-oxa-2-zirconacyclopentanes with an excellent regioselectivity. Carbon—carbon bond formation occurred exclusively at the terminal carbon of vinylsilanes. Their corresponding γ-silylalcohols were obtained after hydrolysis. The products showed that vinylsilanes reacted with carbonyl compounds at the β-carbon to silyl group. It is in sharp contrast to the conventional reactions of vinylsilanes of which the α-carbon normally attacked electrophiles. The reactions of styrene and its derivatives with pentan-3-one on zirconium gave a mixture of two regioisomers. Substituents of alkenes tend to be in α-position to Zr in 1-oxa-2-zirconacyclopentanes. This orientation showed a different aspect of the formation of 1-oxa-2-zirconacyclopentanes from the alkene-alkene coupling reaction on zirconium. The regioselectivity of the reaction with carbonyl compounds decreased in this order; R = alkyl > silyl > aryl.