Synthesis of α‑Boryl Ketones via Hydration or Oxidation of B(MIDA)-Decorated Alkynes

α-Boryl ketones are traditionally challenging targets in organic synthesis. Reported herein is a mild and metal-free synthesis of α-boryl ketones via the hydration or oxidation of N-methyliminodiacetyl boronate (B­(MIDA))-decorated alkynes. A new hydration system comprised of AcCl and H2O in HFIP allows the hydration of arylethynyl B­(MIDA)­s at room temperature with decent functional group tolerance. An oxidative carbon deletion process of propargylic B­(MIDA)­s is also developed for the synthesis of aliphatic α-boryl ketones. An intriguing β-boron effect was observed to account for the unique site- and chemoselectivities. The application of the products in the synthesis of borylated heterocycles was demonstrated.