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Catalyst- and Stoichiometry-Dependent Deoxygenative Reduction of Esters to Ethers or Alcohols with Borane-Ammonia
P Veeraraghavan Ramachandran1, Abdulkhaliq A Alawaed1, Henry J Hamann1
1Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States.
Abstract:
A facile and selective room temperature deoxygenation of both aromatic and aliphatic carboxylic esters to ethers has been achieved by regulating the stoichiometry of the reductant, BH3-NH3, and the catalyst, TiCl4. This first, practical borane-mediated process is compatible with various potentially sensitive functional groups and is applicable to the deoxygenative ether formation from typically challenging aromatic acid esters. Substituting BF3-Et2O as the catalyst alters the reaction pathway, reducing the esters to alcohols. Mechanistic insights are provided by NMR spectroscopy, deuterium labeling, and kinetic isotope studies.
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