Switching Over of the Chemoselectivity: I 2 -DMSO-Enabled α,α-Dichlorination of Functionalized Methyl Ketones.

Precise control of the chemoselectivity of the halogenation of a substrate equipped with multiple nucleophilic sites is highly demanding and challenging. Most reported chlorinations of methyl ketones show poor compatibility or even exclusive selectivity toward electron-rich arene, olefin, and alkyne residues. This is attributed to the direct or in situ employment of electrophilic Cl 2 /Cl + species. Here, we reported that, even bearing those competitive residues, methyl ketones can still undergo dichlorination to afford α,α-dichloroketones in a chemo-specific manner. Enabled by the I 2 -dimethyl sulfoxide catalytic system, in which hydrochloric acid only acts as a nucleophilic Cl - donor, this straightforward dichlorination reaction is safe and operator-friendly and has high atomic economy, giving access to structurally diverse α,α-dichloroketones in good yields and with good functional-group tolerance.