Highly enantioselective [2,3]-Wittigrearrangement of functionalized allyl benzyl ethers was accomplished using a chiral di-tert-butyl bis(oxazoline) ligand. The reaction proceeded with excellent diastereo- and enantioselectivity when no methoxy substituent was present at the ortho-position on the benzyl group. On the other hand, the enantioselectivity was drastically decreased in the presence of an
Asymmetric [2,3]-Wittig Rearrangement of Oxygenated Allyl Benzyl Ethers in the Presence of a Chiral di-<i>t</i>Bu-bis(oxazoline) Ligand: A Novel Synthetic Approach to THF Lignans
allyl benzyl ethers in the presence of a chiral di‐tBu‐bis(oxazoline) ligand. In various oxygenated benzylic ethers, the reactions proceeded with excellent diastereo‐ and enantioselectivities, although the presence of a methoxy substituent at the ortho‐position on the benzyl group drastically decreased the enantioselectivity. Conversely, o‐ethyl and o‐phenyl substituents had no significant effect on
Indium-mediated allylation of carbonyl compounds with an allylic bromide in aqueous media: anomalous syn-diastereoselectivity regardless of allylic bromide geometry
作者:Teck-Peng Loh、Zheng Yin、Hong-Yan Song、Kee-Leng Tan
DOI:10.1016/s0040-4039(02)02773-9
日期:2003.1
Anomalous syn-diastereoselectivity of indium-mediated coupling of aldehydes with bromides Z-3b and E-3b is reported. The reaction afforded high syn selectivity regardless of the allylic bromide geometry. Preliminary studies on the enantioselective indium-mediatedallylation were attempted and found to give the desired products in moderate yield with high syn selectivity and enantioselectivity.