Nickel-catalyzed asymmetric photoenolization/Mannich reaction of (2-alkylphenyl) ketones.

A diastereo- and enantioselective photoenolization/Mannich (PEM) reaction of -alkyl aromatic ketones with benzosulfonimides was established by utilizing a chiral ,'-dioxide/Ni(OTf) complex as the Lewis acid catalyst. It afforded a series of benzosulfonamides and the corresponding ring-closure products, and a reversal of diastereoselectivity was observed through epimerization of the benzosulfonamide products under continuous irradiation. On the basis of the control experiments, the role of the additive LiNTf in achieving high stereoselectivity was elucidated.