Coupling reaction with organocuprates example

Scheme 8.1 gives several examples of the use of coupling reactions of organocuprate reagents with halides and acetates. Entries 1 to 3 are examples of the... 

Coupling reactions with alkyl halides often use large excess of cuprate, as mentioned above, which can be a severe limitation if the halide precursor to the organocuprate is difficult to prepare or unavailable from commercial sources. A solution to this problem is to prepare a cuprate with a ligand that is less reactive, allowing selective transfer of the substituent of choice. An example is the use of 417 in a reaction with 418 that... 

Reaction of the alkenyl iodide with a lithium organocuprate, or with an organometallic species in a palladium-catalysed coupling, gives the corresponding substituted allylic alcohol (in which the substituents originally present in the propargylic alcohol are trans to each other). This method is applicable to a variety of synthetic problems in which the stereoselective introduction of a trisubstituted carbon-carbon double bond is involved. For example, it formed a key step in a synthesis of juvenile hormone (2.64). 

This is a very general reaction in that primary, secondary, and tertiary alkyl halides react with primary, secondary, or tertiary organocuprates. The halide can be a chloride, a bromide, or an iodide, but iodides are more reactive than bromides, which are more reactive than chlorides. Another example is the reaction of 49 with lithium diphenylcuprate to give 50. The reaction of alkyl halides and organocuprates is the preferred method for coupling an alkyl halide to an organometallic compound. Many different hydrocarbons can be prepared. 

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