Highly Enantioselective Allylation of Ketones: An Efficient Approach to All Stereoisomers of Tertiary Homoallylic Alcohols

An optimized protecting group for allylboronates allowed the use of ketones in order to synthesize all isomers of quaternary homoallylic alcohols with high enantioselectivities. All symmetric isomers of the allylboronate were prepared in high yields and diastereoselectivities using S(N)2' reactions. The improved reactivity of the novel protecting group was verified by following the reaction kinetics with H-1 NMR spectroscopy. Mechanistic studies using DFT calculations were conducted to investigate the new findings. Thus, the stereochemical outcome and enhanced reactivity can be rationalized.