[3,3]-Acyloxy Rearrangement-Triggered Regioselective Hydration of δ-Acetoxy-α,β-Alkynoates/Halo Alkynes.

Herein, we report a simple, efficient, highly regioselective, and broad-scope hydration method that is facilitated by an unusual interception of an electrophilic intermediate by water generated via acetate group participation during [3,3]-acyloxy rearrangement. Various carboxylate-directing groups including acetate, acrylates, pivalates, benzoate or its derivatives, and those derived from bioactive natural products were successfully implemented to direct the regioselective hydration for various functionalized δ-acyloxy-β-ketoester synthesis. The reaction pathway was further confirmed by 18O labeling experiments, and to the best of our knowledge, this is the first report of hydration through an electrophilic intermediate generated during [3,3]-acyloxy rearrangement. Synthetic application includes the synthesis of a modifiable C5-carbon chain, five-, six-, and seven-membered heterocycles, and natural product diversification.