Sparteine-Mediated Enantioselective [2,3]-Wittig Rearrangement of Allyl ortho-Substituted Benzyl Ethers and ortho-Substituted Benzyl Prenyl Ethers

摘要

The (-)-sparteine-mediated enantioselective [2,3]-Wittig rearrangement of N,N-dialkyl-o-allyloxymethylbenzamides and o-substituted benzyl prenyl ethers has been investigated. Enantiomeric excess up to 60% was observed as for the reaction with N,N-diethyl-o-allyloxymethylbenzamide. From the mechanistic investigations, it was suggested that the stereoinformation was introduced at the deprotonation step. Substoichiometric amount of (-)-sparteine (0.2 equiv.) did not decrease the enantioselectivity. Introduction of functional groups other than carbamoyl group did not enhance the enantioselectivity in this rearrangement.