Stereocontrol in rare earth metal triflate-catalyzed 1,3-dipolar cycloaddition reaction of 2-benzopyrylium-4-olate with aldehydes
Exo-cycloadduct was obtained with high stereoselectivity by the addition of ytterbium triflate (Yb(OTf)(3)) (10 mol %) in the rhodium(II) acetate (Rh(2)(OAc)(4))-catalyzed decomposition of o-(methoxycarbonyl)-alpha-diazoacetophenone in the presence of benzaldehyde. In the reaction in the absence of Yb(OTf)(3), almost no selectivity was obtained. Stereoselectivity in the reactions with p-nitrobenzaldehyde, p-anisaldehyde, and benzyloxyacetaldehyde could be also controlled to high exo preference by the addition of Yb(OTf)(3).
Suga
H
Department of Chemistry and Material Engineering, Faculty of Engineering, Shinshu University, Wakasato, Nagano 380-8553, Japan, and Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
Kakehi
A
Ito
S
Inoue
K
Ishida
H
Ibata
T