Corey-House Synthesis: Preparation of Unsymmetrical Alkanes

By Chemca Editorial Team • Last Updated: January 2026 • 9 min read

The Corey-House Synthesis is a versatile organometallic coupling reaction used to synthesize alkanes. Unlike the Wurtz reaction, which is limited to symmetrical alkanes, the Corey-House synthesis is excellent for preparing unsymmetrical alkanes with good yields.

1. The General Concept

The reaction involves the coupling of an alkyl halide ($R'-X$) with a Lithium Dialkylcuprate (known as the Gilman Reagent, $R_2CuLi$).

$$ R_2CuLi + R'-X \xrightarrow{\text{Ether}} R-R' + RCu + LiX $$

Where:

$R_2CuLi$: Gilman Reagent (acts as the source of nucleophile $R^-$).
$R'-X$: Substrate Alkyl Halide (must be primary or methyl).
$R-R'$: Desired Alkane Product.

2. Preparation of Gilman Reagent

The reagent is prepared in situ in two steps:

Step 1: Formation of Alkyllithium

An alkyl halide ($R-X$) reacts with Lithium metal in dry ether.

$$ R-X + 2Li \xrightarrow{\text{Dry Ether}} R-Li + LiX $$

Step 2: Formation of Lithium Dialkylcuprate

The alkyllithium reacts with Cuprous Iodide ($CuI$).

$$ 2R-Li + CuI \rightarrow R_2CuLi + LiI $$

3. Mechanism of Coupling

The Gilman reagent reacts with the second alkyl halide ($R'-X$). The reaction follows a pathway similar to the $S_N2$ mechanism, where the alkyl group from the cuprate attacks the alkyl halide.

Key Constraint

For the reaction to proceed efficiently, the substrate alkyl halide ($R'-X$) must be Methyl or Primary ($1^\circ$). If a secondary or tertiary alkyl halide is used as the substrate, Elimination dominates, producing alkenes instead of alkanes.

Example: Synthesis of Propane

Reaction between Lithium Dimethylcuprate and Ethyl Chloride.

$$ (CH_3)_2CuLi + CH_3CH_2Cl \rightarrow \underbrace{CH_3CH_2CH_3}_{\text{Propane}} + CH_3Cu + LiCl $$

4. Advantages over Wurtz Reaction

Feature	Wurtz Reaction	Corey-House Synthesis
Product Type	Only Symmetrical Alkanes (Even C)	Symmetrical & Unsymmetrical (Odd C)
Mixed Reactants	Gives mixture of 3 products (Poor yield)	Gives specific product (High yield)
Versatility	Limited to Alkyl halides	Reagent ($R$) can be Aryl, Vinyl, or Alkyl

5. Important Notes

The alkyl group ($R$) inside the Gilman reagent ($R_2CuLi$) can be $1^\circ$, $2^\circ$, $3^\circ$, aryl, or vinyl.
The alkyl group ($R'$) of the substrate ($R'-X$) must be methyl or $1^\circ$.
This method is ideal for synthesizing alkanes with odd numbers of carbon atoms (e.g., Propane, Pentane).

Corey-House Quiz

Test your concepts on Gilman reagents and alkane synthesis. 10 MCQs with explanations.

Corey-House Synthesis: Mechanism & Gilman Reagent | Chemca