SN2 reaction of organocuprates (Gilman reagents) with alkyl halides to give alkanes

by James

Description: Alkyl halides (or tosylates) will react with organocuprates (Gilman reagents) to form alkanes in an SN2 reaction
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Notes: X here is a halide (Cl, Br, I) or sulfonate (OTs, OMs)

Also note that this can be a very useful way of forming carbon-carbon bonds.

Examples: 

Notes: The byproduct of all of these reactions is the lithium salt (e.g. LiBr) and the organocopper species (e.g. CH3Cu).

Mechanism: This reaction is actually a fairly straightforward SN2 reaction, with breakage of the C–Cu bond accompanying attack at the alkyl halide (Step 1, arrows A and B).

Notes: Again note that this forms a carbon-carbon bond. This is important as there aren’t too many reactions that do so, through an SN2 (another example is the reaction of alkyl halides with acetylide ions).

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{ 3 comments… read them below or add one }

Petr Menzel

Hi, please for explaining how is created bond C1 and C2 in Mechanism? C1 is (+) and Cu is (-) —> C2 is (+) I suppose. Thx. P.

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James

That is correct. C-2 attached to Cu is nucleophilic (partially negative) and C1 attached to Br is electrophilic (partially positive).

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Petr Menzel

Oh, my mistake. Electronegativity (Cu) = 1,9 < Electronegativity (C) = 2,5. :-) Thx

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