[Chemistry Class Notes] on Corey House Reaction Pdf for Exam

The coupling process is a good approach to synthesize higher alkanes by joining two alkyl groups together. The Corey-House reaction is the name for this adaptable approach.

Organic reactions are chemical processes in which organic substances are involved. Addition reactions, elimination reactions, sublimation processes, pericyclic reactions, and rearrangement reactions are the most common types of organic chemistry reactions.

When the Gilman reagent is combined with an alkyl halide, it produces an alkane with a greater carbon number than the initial alkyl halide. The Corey-House reaction is useful and common in organic synthesis, however, it is confined to a 1o alkyl halide, whereas the Gilman reagents can have 1o, 2o, or 3o alkyl groups.

Synthesis of Corey-House

Alkyl lithium is formed when alkyl halides combine with lithium in dry ether.

R-X + 2Li ⇾ R-Li + LiX

This alkyl lithium combines with CuI to produce Gilman reagent, which is Dialkyl Lithium Cuprate.

2R-Li + CuI ⇾ R2CuLi + LiI

The Corey-House synthesis occurs when dialkyl lithium cuprate combines with an alkyl halide to produce an alkane.

R2CuLi + R’-X ⇾ R-R’ + R-Cu + LiX

R’-X can be methyl halide, p-alkyl halide, or sec alkyl halide in this reaction. Dialkyl lithium cuprate’s alkyl group might be methyl, primary, secondary, or tertiary.

Dialkyl lithium cuprate reacts with aryl halide, alkyl halide, and vinyl halide in this reaction.

Mechanism

Alkyl halide interacts with lithium metal and forms the alkyl lithium complex R-Li when dissolved in dry ether.

R-X can be a primary, secondary, or tertiary alkyl halide in this case.

R-X + 2Li →R-Li + LiX

The reaction of alkyl-lithium with cuprous iodide (CuI) forms lithium Dialkyl Cuprate in the second stage.

Gilman Reagents are the name for this reaction.

2RLi + CuI → R2CuLi +LiI

Importance of Corey-House Synthesis

This approach is superior to the Wurtz reaction. To make a higher hydrocarbon, an alkyl halide and a lithium dialkyl copper are combined.

R’-X + R2-CuLi ⇾ R-R’ + R-Cu + LiX

(R and R’ might or might not be the same person.)

As an example,

CH₃CH₂CH₂Br + (CH₃)₂CuLi ⇾ CH₃CH₂CH₂CH₃ + CH₃Cu + LiBr

This reaction is famous for its ability to produce symmetrical, unsymmetrical, straight chain, and branched-chain alkanes.

The alkyl halide utilized should be primary for a better yield, whereas lithium dialkyl copper can be primary, secondary, or tertiary.

The reaction of an alkyl halide with a lithium dialkyl cuprate to form a new alkane, an organocopper compound and a lithium halide is Corey house synthesis. It is useful to synthesize alkane with an odd number of carbons that are not possible with the Wurtz reaction in which a mixture of alkanes is formed. If we are considering tertiary alkyl halide for a reaction then due to the steric hindrance of three alkyl groups sn2 reaction, substitution does not take place instead there exists a greater possibility of elimination reaction, leading to elimination product. The R part of R2CuLi acts as a strong conjugate base and this leads to elimination.

Corey House Synthesis Mechanism

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Organic reactions are chemical reactions involving chemical compounds. Basically in this Corey synthesis, this reaction occurs in three steps:-

• The lithium metal is treated with an alkyl halide and solvated in dry ether, which converts the alkyl halide into an alkyl lithium compound, R-Li. The starting (R-X)compound  can be primary, secondary, or tertiary alkyl halide:

R-X + 2Li → R-Li + Li-X

• The second step requires cuprous (CuI) treated with an alkyl lithium compound. This creates a lithium dialkyl cuprate compound. These compounds were first synthesized by Henry Gilman of Iowa State University, and are usually called Gilman reagents in honour of his contributions:

2RLi + CuI → R2CuLi + LiI

R’-X + R2CuLi → R-R’ + RCu + LiX

• Cross-products are formed If the second alkyl halide is not the same as the first.

• For this reaction to work successfully it is important to note that the second alkyl halide must be a methyl halide, benzyl halide, primary alkyl halide, or a secondary cycloalkyl halide. For synthesizing organic compounds the relative simplicity of this reaction makes it a useful technique.

• As R and R’ are different then it is important to note that only the cross product obtained is R–R’. but both the products i.e R–R or R’–R’ are not formed in significant quantities. An example of a cross-coupling reaction is Corey house reaction. The Corey–House synthesis is one of the earliest transition metal-mediated (or catalyzed) cross-coupling reactions to be discovered.
  

More about Importance of Corey House Synthesis

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Corey House is a powerful and practical tool for the synthesis of complex organic molecules. This reaction usually takes place at room temperature. 

• One of the features of Corey house synthesis is that the operation is a very simple, easily accessible reaction. It can be used for preparing straight-chain, branched-chain, symmetrical, or unsymmetrical alkanes. For a better product, the alkyl halide used should be primary.

• In the case of tosylates and alkyl bromides when a configurationally pure alkyl electrophile is used, inversion of configuration is observed. To give a copper(III) species the reaction is believed to process via sn-2 like mechanism which undergoes reductive elimination to give the coupling product.

• When alkyl iodides are used and cyclization products are observed, the scrambling of configuration is also observed to form for alkyl iodides with an olefin tether, both of which are indicative of the involvement of radicals.

• For this reaction to work successfully the alkyl (pseudo)halide coupling partner must be methyl, benzylic, allylic, 1° alkyl, or 2° cycloalkyl. In most cases, acyclic 2° electrophiles and 3° give unsatisfactory results. (However, see below for recent modifications that allow 2° electrophiles to be used successfully).

• On the other hand, sterically hindered organocopper reagents, including 3° and other branched alkyl reagents, are generally tolerated, However, aryl bromides, iodides, and sulfonates, which do not ordinarily undergo nucleophilic substitution in the absence of a transition metal, can be used successfully as coupling partners.