Low-Temperature\nBorylation of C(sp<sup>3</sup>)–O\nBonds of Alkyl Ethers by Gold–Metal Oxide Cooperative Catalysis

Since ether moieties are often found\nnot only in petrochemical\nproducts but also in natural organic molecules, the development of\nmethods for manipulating C–O bonds of ethers is important for\nexpanding the range of compound libraries synthesized from biomass\nresources, which should contribute to the goal of carbon neutrality.\nWe report herein that gold nanoparticles supported on Lewis acidic\nmetal oxides, namely α-Fe<sub>2</sub>O<sub>3</sub>, showed excellent\ncatalytic activity for the reaction of dialkyl ethers and diborons,\nwhich enables the conversion of unactivated C(sp<sup>3</sup>)–O\nbonds to C(sp<sup>3</sup>)–B bonds at around room temperature.\nVarious acyclic and cyclic ethers as well as a series of diborons\nparticipated in the heterogeneous gold-catalyzed borylation of unactivated\nC(sp<sup>3</sup>)–O bonds, to give a series of alkylboronates\nin high yields. Mechanistic studies corroborated that the present\nborylation of C(sp<sup>3</sup>)–O bonds of dialkyl ethers proceeded\nat the interface between gold nanoparticles and Lewis acidic metal\noxides. Furthermore, adsorption IR measurements supported the notion\nthat strong Lewis acid sites were generated at the boron atom of diborons\nadsorbed at the interface between Lewis acidic metal oxides and gold\nnanoparticles, which enabled us to ensure that the cooperation of\ngold nanoparticles and Lewis acidic metal oxides was responsible for\nthe efficient transformation of unactivated C(sp<sup>3</sup>)–O\nbonds in ethers under mild conditions. This novel reaction technology\nwhich is specific to heterogeneous catalysts enables the activation\nof stable C(sp<sup>3</sup>)–O bonds of oxygenated chemical\nfeedstock, which is beneficial for the sustainable synthesis of value-added\norganoboron compounds.