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Reduction of gallic acid by in situ BH
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Orientador(es)
Resumo(s)
Lithium aluminum hydride (LiAlH₄, LAH) is one of the most widely used reducing agents in organic synthesis due to its high reactivity and broad applicability. It effi-ciently reduces carbonyl-containing compounds such as esters, carboxylic acids, amides, and nitriles to the corresponding alcohols or amines, whereas sodium borohydride (NaBH₄) is generally limited to reducing aldehydes and ketones1 under mild conditions. The superior reactivity of LAH arises from the highly po-lar Al-H bond, which enables hydride transfer to less reactive carbonyl groups.2 However, LAH presents important drawbacks: it is highly moisture-sensitive, reacts violently with water or protic solvents, and re-quires strictly anhydrous conditions, aprotic solvents such as THF or diethyl ether, and an inert atmosphere. On the other hand, some studies are shown a new al-ternative to use NaBH4 in the presence of an electro-phile, as iodine, generating new alternatives to the use of LAH.3 This work presents a safer and more conve-nient alternative for the reduction of carboxylic acids using gallic acid as a model substrate. The methodolo-gy employs NaBH₄ in the presence of boron trifluoride diethyl etherate (BF₃·Et₂O), which generates borane (BH₃) in situ, a much stronger reducing species capable of efficiently converting carboxylic acids into primary alcohols.4 Compared with LAH, this approach offers milder reaction conditions, improved operational safe-ty, and easier handling, since in situ generation of BH₃ avoids direct manipulation of highly reactive reducing agents while maintaining high reduction efficiency. The reduction of gallic acid is particularly significant due to its multiple hydroxyl groups and the sensitivity of the aromatic structure, making selectivity essential. Controlled addition of gallic acid to the BH₃ solution proved effective for conversion into 3,4,5-trihydroxy-benzyl alcohol while minimizing possible interactions between free BF₃ and phenolic groups. Overall, this methodology represents a practical and valuable al-ternative for safer and milder organic reductions with good functional-group tolerance.
Descrição
Palavras-chave
Gallic acid Phenolic acids Phenolic alcohols
Contexto Educativo
Citação
Silva, R. P., Prudêncio, C., & Vieira, M. (2026). Reduction of gallic acid by in situ BH. Book of Abstracts of the 8th Meeting on Medicinal Biotechnology, 48. https://edicoes.ipp.pt/index.php/books/catalog/book/251
Editora
Politema