Hypervalent-Iodine-Mediated Base-Free Oxidative Olefination of Benzylic Amines to Access α,β-Unsaturated Ketones

We report a one-pot base-free protocol for the oxidative olefination of benzylic amines promoted by a hypervalent iodine reagent for the synthesis of α,β-unsaturated ketones. Mechanistically, (diacetoxyiodo)benzene oxidizes the benzylic amine to the corresponding imine, which, on reaction with a phenacyl(triphenyl)phosphonium bromide salt and an in situ generated acetoxy anion leads to an α,β-unsaturated ketone. A wide range of α,β-unsaturated ketones were easily accessed through direct oxidative olefination of substituted benzylic amines in good to excellent yields and with high E-selectivity.