Borylation of Stable C(sp3)-O Bonds of Alkyl Esters over Supported Au Catalysts
Masafumi Doi, Hiroki Miura*, Tetsuya Shishido*
*Tokyo Metropolitan University, 1-1 minami-Osawa, Hachioji,
Tokyo 192-0397, Japan, Email: miura-hiroki
tmu.ac.jp,
shishido-tetsuyatmu.ac.jp
M. Doi, H. Miura, T. Shishido, Org. Lett., 2024, 26, 2902-2907.
DOI: 10.1021/acs.orglett.4c00225
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Abstract
Supported gold catalysts efficiently promote the borylation of stable C(sp3)-O bonds of alkyl esters. The use of a disilane as an electron source and gold nanoparticles as a single-electron transfer catalyst is the key to generating alkyl radicals. A subsequent cross-coupling with bis(pinacolato)diboron affords the desired alkyl boronates.
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proposed mechanism
Details
The document discusses a study on the borylation of stable C(sp3)−O bonds of alkyl esters using supported gold (Au) catalysts. The research, published in Organic Letters, highlights the efficiency of Au catalysts in promoting the borylation process, which is crucial for synthesizing alkyl boronates, valuable building blocks in organic synthesis. The study utilized disilane as an electron source and gold nanoparticles for single-electron transfer, generating alkyl radicals via homolysis of C(sp3)−O bonds. The reaction between bis(pinacolato)diboron and various alkyl esters, including linear, cyclic, and secondary alkyl acetates, yielded diverse alkyl boronates. The optimal conditions involved using ZrO2-supported Au catalysts and toluene as the solvent at 100°C. The study found that other metal catalysts like Ni, Cu, Pd, Ag, or Pt were ineffective. The Au/ZrO2 catalyst demonstrated high reusability and scalability, maintaining efficiency over multiple runs. Mechanistic studies suggested that the formation of alkyl radicals and silyl radicals is key to the borylation process. The research opens avenues for further exploration of substrate scope and detailed mechanistic understanding, contributing to advancements in organic synthesis and carbon-neutral chemistry.
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ID: J54-Y2024
