Copper-Catalyzed Borocarbonylative Coupling of Internal Alkynes with Unactivated Alkyl Halides: Modular Synthesis of Tetrasubstituted β-Borylenones

Reported is a general procedure to synthesize tetrasubstituted enones, which are borylated in the beta-position, using a copper-catalyzed four-component coupling reaction of simple chemical feedstocks: internal alkynes, alkyl halides, bis(pinacolato)diboron (B(2)pin(2)), and CO. A broad scope of highly functionalized beta-borylated enones, a largely unknown class of organic compounds, can be accessed efficiently using this method. The synthesis of all-carbon tetrasubstituted enones was realized by employing the beta-borylated enone unit, without purification, in a Suzuki-Miyaura coupling. The utility of the method was further demonstrated by various transformations, including halogenation, oxidation, and protodeboration, of the corresponding reduced oxaborole species to provide densely substituted allylic alcohol and ketone products.