Rhodium-Catalyzed [6+2] Cycloaddition of Alkynylboronates with 4-Allenals for the Synthesis of Multisubstituted Eight-Membered Ketones

We report a one-pot synthesis of multisubstituted eightmembered ketones via a rhodium-catalyzed [6+2] cycloaddition of 4allenals with alkynylboronates, followed by Suzuki-Miyaura coupling.The inherently unstable boronic ester intermediates are directly engaged in the coupling, enabling in situ derivatization. Alternatively, these intermediates can be converted into stable pinacol boronates upon treatment with pinacol, which serve as versatile intermediates for further functionalization.