Alkyl halides coupling

Electrophiles may be alkylating and acylating agents and C02. Tertiary alkyl halides couple more efficiently than primary. The following examples illustrate the scope.39 55... 

Coupling of R Br(Cl) with R2SnBu. 2 Alkyl halides couple with 2-(tributyl-stannyl-4,4-dimethyl-2-oxazoline (2) in the presence of this Pd catalyst (equation... 

Burdon et al. 31) have proposed that aryl and vinyl halides, but not alkyl halides, couple with copper compounds via a four-center transition state (XI). Nucleophilic substitution of vinylic bromides by organo-... 

Mechanism for Cu-cataiyzed alkyl halide coupling showing a Cu(lll) intermediate. 

Although rare, the direct C-H alkylation of p)fridine is known with both alkene and alkyl halide coupling partners in the... 

This zinc-copper couple reacts with methanol, the mixture reducing an alkyl halide to an alkane ... 

Two mechanisms have been proposed for the Wurtz reaction (compare Section III,7) and for the Wurtz-Fittig reaction. According to one, sodium reacts with the alkyl halide to produce a sodium halide and a free radical, which subsequently undergoes coupling, disproportionation, etc. ... 

The most interesting and difficult cross-coupling is alkyl-alkyl coupling, because oxidative addition of alkyl halides having /i-hydrogen is slow. In addition, easy elimination of /d-hydrogen is expected after the oxidative addition. 

The most frequently used organocuprates are those m which the alkyl group is pri mary Steric hindrance makes secondary and tertiary dialkylcuprates less reactive and they tend to decompose before they react with the alkyl halide The reaction of cuprate reagents with alkyl halides follows the usual 8 2 order CH3 > primary > secondary > tertiary and I > Br > Cl > F p Toluenesulfonates are somewhat more reactive than halides Because the alkyl halide and dialkylcuprate reagent should both be primary m order to produce satisfactory yields of coupled products the reaction is limited to the formation of RCH2—CH2R and RCH2—CH3 bonds m alkanes... 

Preparation of alkanes using lithium di alkylcuprates (Section 14 11) Two alkyl groups may be coupled together to form an alkane by the reaction of an alkyl hal ide with a lithium dialkylcuprate Both alkyl groups must be primary (or meth yl) Aryl and vinyl halides may be used in place of alkyl halides... 

Coupling of alkyl halides with Na, supplanted by the coupling ol alkyl halides or sulfonates with Gngnard reagents or RLi in the presence of CufI) salts... 

Another type of Grignard reaction is the alkylation with alkyl halides. Upon treatment of a Grignard reagent RMgX with an alkyl halide 5, a Wwrtz-like coupling reaction takes place. 

The coupling of alkyl halides 1 upon treatment with a metal, e.g. elemental sodium, to yield symmetrical alkanes 2, is called the Wurtz reaction. Aryl alkanes can be prepared by the Wurtz-Fittig reaction, i.e. the coupling of aryl halides with alkyl halides. 

The synthetic applicability is rather limited, due to the various side-reactions observed, such as eliminations and rearrangement reactions. The attempted coupling of two different alkyl halides in order to obtain an unsymmetrical hydrocarbon, usually gives the desired product in only low yield. However the coupling reaction of an aryl halide with an alkyl halide upon treatment with a metal (the Wurtz-Fittig reaction) often proceeds with high yield. The coupling of two aryl halides usually does not occur under those conditions (see however below ) since the aryl halides are less reactive. 

This organometallic coupling reaction is useful in organic synthesis because it forms carbon-carbon bonds, thereby making possible the preparation of larger molecules from smaller ones. As the following examples indicate, the coupling reaction can be carried out on aryl and vinylic halides as well as on alkyl halides. 

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