Coupling of alkyl halides with organometallic compounds

Fig. 1 Iron-catalyzed cross-coupling of alkyl halides with organometallic compounds...

The coupling of alkyl halides with organometallic compounds is the only one of these methods in which carbon-carbon bonds are formed and a new, bigger carbon skeleton is generated. 

Netherton MR, Fu GC. Nickel-catalyzed cross-couplings of unactivated alkyl halides and pseudohalides with organometallic compounds. Adv. Synth. Catal. 2004 346 1525-1532. 

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. 

A variety of organometallic compoundshave been used to couple with alkyl halides. " Organosodium and organopotassium compounds are more reactive than Grignard reagents and couple even with less reactive halides. Organolithium... 

The same electrochemical process was also used for the coupling between aldehydes or ketones and activated alkyl halides such as a-chloroesters, -nitriles, and -ketones as well as aya-dichloroesters.334 Electroanalytical studies have shown initial electroreduction of Fe(n) to Fe(i) and subsequent formation of an iron organometallic intermediate (e.g., a 7t-allyliron complex in Equation (27)) before reaction with the corresponding carbonyl compounds.335... 

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