Copper-Catalyzed Chemo-, Regio-, and Stereoselective Ring-Opening sp2/sp3 Diborylation of Arylidenecyclopropanes

A copper-catalyzed sequential hydroboration/isomerization/boryldemetalation reaction of arylidenecyclopropanes (ACPs) is reported, furnishing a straightforward and efficient route for the assembly of valuable 1,3-diboronates featuring both sp2/sp3 C–B bonds. In contrast to the established CuH-induced ring-opening cascade hydrofunctionalizations of ACPs, which afford diverse sp3/sp3 1,n-diboronates, silylboronates, or aminoboronates, CuBpin species-catalyzed diborylation variant remains unexplored. Particularly, the envisioned ring-opening regioselective hydroboration followed by boryldemetalation of homoallylic copper intermediates to concurrently construct both sp2- and sp3-hybridized C–B bonds in a one-pot transformation represents a significant knowledge gap in this field. Herein, we present the Cu-catalyzed chemo-, regio-, and stereoselective ring-opening sp2/sp3 diborylation of ACPs. Control experiments are conducted to illustrate the flexible transformation of Cu–H into Cu–Bpin and the essential significance of NaBEt3H in this transformation. The synthetic practicality of our presented protocol is further demonstrated by gram-scale preparation within a short period and the selective derivatization of the two types of boron moieties, enabling access to diversified high-valued 1,n-diboron compounds (n = 3, 5, 6), β-hydroxy ketones, 1,3-diols, α,β-unsaturated ketones, thermodynamically unstable cis-homoallylic boronate, and cis-homoallylic alcohol.