Grignard reagents alkanes

The coupling of alkyl Grignard reagents with alkyl iodides to afford alkanes by use of dppf as a ligand has been reported[449], but re-examination of the reaction has shown that only reduction takes place, and no coupling was observed[450]. 

Hydroperoxides have been obtained from the autoxidation of alkanes, aralkanes, alkenes, ketones, enols, hydrazones, aromatic amines, amides, ethers, acetals, alcohols, and organomineral compounds, eg, Grignard reagents (10,45). In autoxidations involving hydrazones, double-bond migration occurs with the formation of hydroperoxy—azo compounds via free-radical chain processes (10,59) (eq. 20). 

We do not list the many hydrolyses of sodium or potassium enolates, and so on, found in Organic Syntheses. The hydrolysis of a Grignard reagent to give an alkane is found at OS II, 478 the reduction of a vinylic tin compound at OS VIII, 381 and the reduction of an alkynylsilane at OS VIII, 281. 

The carbanion equivalent from a Grignard reagent is also a strong base. pATa values for alkanes are typically about 50, and for aromatics about 44. Not surprisingly, a Grignard reagent reacts readily with... 

Alkanes can also be prepared from alkyl halides by reduction, directly with Zn and acetic acid (AcOH) (see Section 5.7.14) or via the Grignard reagent formation followed by hydrolytic work-up (see Section 5.7.15). The coupling reaction of alkyl halides with Gilman reagent (R 2CuLi, lithium organocuprates) also produces alkanes (see Section 5.5.2). 

Fluorine can be introduced into alkanes indirectly by treating either lithium or Grignard reagents with fluorine (Fig. 70) [165] at -60°C in hydrocarbon ether solvents. The lithium reagents reacted more rapidly than the corresponding Grignard reagents, and primary or secondary alkyl compounds were more reactive than tertiary. 

Although of relatively weak acidity, amines will react with either carbanionic metal alkyls or hydridic metal hydrides to form amides with the elimination of alkane or hydrogen, respectively. The easiest and most exploited method for the synthesis of lithium and magnesium amides is to treat lithium alkyls or Grignard reagents (normally commercially available) with the corresponding amine (equations 25,47 264 and 2749). 

Considering the problem retrosynthetically, we can see that a key intermediate having the carbon skeleton of the desired product is 3-methyl-3-pentanol. This becomes apparent from the fact that alkanes may be prepared from alkenes, which in turn are available from alcohols. The desired alcohol may be prepared from reaction of an acetate ester with a Grignard reagent, ethylmagnesium bromide. 

Once the alkyl bromide is in hand, it may be converted to an alkane by conversion to a Grignard reagent followed by addition of water. 

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