Chemoselective Ketone Synthesis by the Strontium‐mediated Alkylation or Arylation of N,N‐Dimethylamides or Urea.

Ketone synthesis via the addition of organometallic reagents to amides has long been investigated. In many cases, it is necessary to control the solvent, reaction temperature, and adhere to strict nucleophile stoichiometry for each combination of amide and organometallic reagent. Strontium, with an electronegativity comparable to lithium but a larger ionic radius, may display high reactivity with the characteristics of monoalkylation. Here, we show that the monoalkylation of various N,N-dimethylamide derivatives with alkyl iodides to afford the ketones proceeds smoothly under generally mild temperature conditions. By this method, not only aromatic amides but also α-proton-bearing aliphatic amides were suitable substrates for ketone synthesis. In addition, we found that tetramethylurea, typically a poor electrophile, also reacted to afford benzophenone in good yield with excellent selectivity.