Nanoporous Gold Catalyzed Borylation of C(sp³)–O Bonds in Dialkyl Ethers and Mechanistic Elucidation

Selective cleavage and functionalization of C–O bonds in ethers are a longstanding challenge in organic synthesis due to their inherent stability. This is particularly significant for synthesizing alkylboron compounds, which serve as versatile intermediates in diverse transformations. However, the high chemical stability of dialkyl ethers makes their successful borylation rare. Herein, we present a heterogeneous catalytic borylation of various dialkyl ethers with B2pin2 using an unsupported nanoporous gold catalyst (AuNPore). The nanosized, sponge-like catalyst operates without the need for metal oxide supports or bases, efficiently converting a wide range of acyclic and cyclic ethers, as well as acetals, into alkyl monoboronates and diboronates. Mechanistic studies indicate that AuNPore promotes B–B bond cleavage, leading to deoxygenative carbocation formation. This enables an unprecedented borylation pathway via the formation of a C(sp3)–Au–Bpin organogold species, which undergoes reductive elimination to yield alkylboron products.