Lewis-acid mediated allylations of β-alkoxy N-tosyl imines lead to 3-alkoxy homoallylic N-tosyl amines with anti diastereoselectivity. Diastereoselectivity and yields of reactions are comparable between two methods of Hosomi-Sakurai allylations. Observed selectivity trends and computational evidence suggest that 1,3 asymmetric induction occurs through the formation of a six- membered ring chelate which adopts a half-chair-like conformation. The product ratios of allylations to β-alkoxy N-tosyl imines are dependent on conformation preferences of the chelate and stereoelectronic interactions in the transition-state structures. Debenzylation and detosylation of these allylation products result in anti 1,3-amino alcohols, a privileged motif in synthetic and natural bioactive compounds.
1,3-Asymmetric Induction in Diastereoselective Allylations of Chiral N-Tosyl Imines