Direct preparation of allylic zirconium reagents from zirconocene-olefin complexes and alkenes.
A novel method for preparation of allylic zirconium reagents directly from 1-alkenes via zirconocene-olefin complex has been developed. Selective transfer of the hydride of zirconocene allyl hydride complex, a tautomer of zirconocene-olefin complex, to diisopropyl ketone generates the corresponding zirconocene alkoxide allyl. The allylic zirconium reagents formed effects stereoselective allylation of aldehyde at 25 degrees C and -78 degrees C to provide syn- and anti-homoallyl alcohols, respectively. The anti-isomer is formed via a six-membered chair transition state under kinetic control. The syn-selectivity can be rationalized by considering isomerization of the anti-adduct by a retroallylation process.
Fujita
Kazuya
K
Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
Yorimitsu
Hideki
H
Shinokubo
Hiroshi
H
Oshima
Koichiro
K