Copper-catalyzed borylative cyclization of 1,n-enynyl phosphates leading to five- to eight-membered cyclic 1,4-dienyl boronates

We report here a room temperature, efficient, and broadly applicable copper-catalyzed borylative cyclization of 1,n-enynyl (n = 6–9) phosphates for the concise synthesis of structurally diverse 5–8 membered cyclic 1,4-dienyl boronates, which represents the first Cu-catalyzed formal intramolecular alkyne allylboration. Subsequent Suzuki-Miyaura coupling provides a facile access to cyclized 1,4-dienes. A mechanism consisting of alkyne borylcupration, intramolecular alkene addition, and β-elimination has been proposed to explain the experimental results.