Bis(oxazoline)–ligand-mediated asymmetric [2,3]-Wittig rearrangement of benzyl ethers: reaction mechanism based on the hydrogen/deuterium exchange effect
asymmetric [2,3]-Wittig rearrangement of allyl benzyl ether in the presence of a bis(oxazoline) chiral ligand [(S,S)-Box–tBu] by comparing the reaction of both enantiomers of monodeuterated benzyl ether 1a–d. As a result, we found that chirality was induced via enantioselective deprotonation followed by efficient chirality transfer of the resulting chiral benzyl carbanion with the inversion of stereochemistry
我们通过比较反应,研究了在双(恶唑啉)手性配体[(S,S)-Box- t Bu]存在下烯丙基苄基醚的不对称[2,3] -Wittig重排中的手性诱导机理。氘代苄基醚1a - d的两种对映体的组成。结果,我们发现手性是通过对映选择性去质子化诱导的,然后通过立体化学的反转有效地手性转移所得的手性苄基碳负离子。揭示了手性配体促进选择性去质子化并防止手性碳负离子消旋化。此外,我们检查了o的影响苯环上的-甲氧基取代基。
Total Synthesis of Eupomatilones 1, 2, and 5 by Enantioselective [2,3]-Wittig Rearrangement
In this study, the asymmetric total synthesis of eupomatilones 1, 2, and 5 has been accomplished. These compounds are lignan congeners containing a biaryl system bearing an α-methylene γ-lactone. They were isolated from the Australian shrub Eupomatia bennettii. Two chiral centers were constructed enantioselectively by the asymmetric [2,3]-Wittig rearrangement of highly oxygenated biaryl compounds,