Sparteine-mediated enantioselective [2,3]-Wittig rearrangement of allyl ortho-substituted benzyl ethers and ortho-substituted benzyl prenyl ethers

Article abstract of DOI:10.1016/S0040-4020(99)00338-5

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-allyloxymetylbenzamide. 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.