Reduction of nitriles to primary amines with LiAlH4

by James

Description: Lithium aluminum hydride [but NOT sodium borohydride (NaBH4)] can reduce nitriles to primary amines.
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{ 6 comments… read them below or add one }

Kapil

GOOD WEBSITE FOR LEARNING

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Matthew Granger

For step 2. Instead of N- getting a second negative charge N (2-), would it first protonate itself once? and then repeat from there until it left?

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James

Hey Matt – although N is drawn with a second negative charge in practice it will be bound to aluminum [an excellent Lewis acid], and the Al-N bond will be quite strong so it’s not as “naked” as it appears. There aren’t really any proton sources present to protonate the nitrogen at this stage until workup.

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Matthew Granger

Yeah, that makes sense, basically the electron density of N is being donated to Al, resulting in less anionic nature as observed.
Thanks James!

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Samuel Anderson

Very misleading. Sodium borohydride is regularly employed to reduce nitriles in combination with transition metals (e.g. Ni, Co).

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James

But that’s not the same as NaBH4 – that’s in situ formation of nickel or cobalt hydride! Completely different. Also – keep in mind that this is written for introductory organic students who encounter NaBH4 and LiAlH4 but will never encounter NaBH4 in the presence of nickel or cobalt salts.

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