Controlled Reduction of Tertiary Amides to the Corresponding Alcohols, Aldehydes, or Amines Using Dialkylboranes and Aminoborohydride Reagents

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• 作者：Christopher L. Bailey ; Alexander Y. Joh ; Zefan Q. Hurley ; Christopher L. Anderson ; Bakthan Singaram
• 刊名：Journal of Organic Chemistry
• 出版年：2016
• 出版时间：May 6, 2016
• 年：2016
• 卷：81
• 期：9
• 页码：3619-3628
• 全文大小：560K
• 年卷期：0
• ISSN：1520-6904

文摘

Dialkylboranes and aminoborohydrides are mild, selective reducing agents complementary to the commonly utilized amide reducing agents, such as lithium aluminum hydride (LiAlH₄) and diisobutylaluminum hydride (DIBAL) reagents. Tertiary amides were reduced using 1 or 2 equiv of various dialkylboranes. The reduction of tertiary amides required 2 equiv of 9-borabicyclo[3.3.1]nonane (9-BBN) for complete reduction to give the corresponding tertiary amines. One equivalent of sterically hindered disiamylborane reacts with tertiary amides to afford the corresponding aldehydes. Aminoborohydrides are powerful and selective reducing agents for the reduction of tertiary amides. Lithium dimethylaminoborohydride and lithium diisopropylaminoborohydride are prepared from n-butyllithium and the corresponding amine-borane. Chloromagnesium dimethylaminoborohydride (ClMg⁺[H₃B-NMe₂]⁻, MgAB) is prepared by the reaction of dimethylamine-borane with methylmagnesium chloride. Solutions of aminoborohydride reduce aliphatic, aromatic, and heteroaromatic tertiary amides to give the corresponding alcohol, amine, or aldehyde depending on the steric requirement of the tertiary amide and the aminoborohydride used.