Peter T. Gallagher, James C. A. Hunt, Andrew P. Lightfoot and Christopher J. Moody
A series of benzaldoxime ethers PhCHNOCHRPh 5 bearing a
chiral auxiliary on oxygen have been prepared to investigate the effect
of the auxiliary on the diastereoselectivity of the addition of
butyllithium to the oxime C
N bond. By increasing the size of the
alkyl group R in the auxiliary, OCHRPh, an increase in de is observed,
with the best compromise between ready availability and high levels of
asymmetric induction in the product 6 being achieved with the oximes
derived from O-(1-phenylbutyl)hydroxylamine.