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.