Reduction of N-Allylamides by LiAlH4: Unexpected Attack of the Double Bond with Mechanistic Studies of Product and Byproduct Formation

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• 作者：Birk Thiedemann ; Christin M. L. Schmitz ; Anne Staubitz
• 刊名：Journal of Organic Chemistry
• 出版年：2014
• 出版时间：November 7, 2014
• 年：2014
• 卷：79
• 期：21
• 页码：10284-10295
• 全文大小：673K
• ISSN：1520-6904

文摘

The reduction of secondary allyl amides with LiAlH₄ can lead to a concomitant reduction of the double bond. Previously, an excess of LiAlH₄ in hazardous solvents was used for the reduction. This work discusses optimized reaction conditions in tBuOMe as a safe solvent, with only a 1.5-fold excess of LiAlH₄, without reduction of the double bond in most cases. ¹H and ²D NMR spectroscopic studies give evidence for the mechanism of the reduction of the amide as well as the double bond: Amide reduction generally precedes double bond reduction. Sterically hindered allylamides are an exception. They are reduced considerably more slowly at higher temperatures, and double bond reduction is observed before amide reduction has gone to completion.