An Isothiourea-Catalyzed Asymmetric [2,3]-Rearrangement of Allylic Ammonium Ylides
摘要:
Benzotetramisole promotes the catalytic asymmetric [2,,3]-rearrangement of allylic quaternary ammonium salts (either isolated or prepared in situ from p-nitrophenyl bromoacetate and the corresponding allylic amine), generating syn-alpha-amino acid derivatives with excellent diastereo- and enantioselectivity (up to >95:5 dr; up to >99% ee).
diastereoselective method was developed for the [2,3]-sigmatropic rearrangement of N-allyl ammonium ylides, affording products in up to 95% isolated yields and up to 97:3 dr; most of the desired products were formed within 1 minute. For the asymmetric reaction, a chiral auxiliary was introduced to the starting compound, affording the rearrangement product with high diastereoselectivities. A rapid and diastereoselective