Copper-catalyzed 1,2-Borylacylation of 1,3-Enynes: synthesis of β-Alkynyl ketones.

A copper catalyzed 1,2-borylacylation of 1,3-enynes with B2pin2 and acid chlorides has been developed. Using readily available 1,3-enynes, B2pin2 and acid chlorides as substrates, a range of highly functionalized α,α-disubstituted β-alkynyl ketones were readily prepared under mild conditions in moderate to good yields. The borylacylated products can be easily derivatized to give several valuable structures. Notably, treatment of the products with NaBO3·4H2O provided 1,2-allenyl ketones, which is proposed to proceed via a retro-aldol process of the corresponding homopropargyl alcohols.