Neopentyl chloride, alkylation with

Alkyl sulfates, tosylates, and other esters of sulfuric and sulfonic acids can be converted to alkyl halides with any of the four halide ions.979 Neopentyl tosylate reacts with Cl, Br, or I without rearrangement in HMPA.980 Similarly, allylic tosylates can be converted to chlorides without allylic rearrangement by reaction with LiCl in the same solvent.981 Inorganic esters are intermediates in the conversion of alcohols to alkyl halides with SOCl2, PC15, PC13, etc. (0-67), but are seldom isolated. 

The complex nature of alkylation of alkenes is illustrated by the reaction of 1- and 2-chloropropane with ethylene,53 which does not yield the expected isopentyl chloride. Instead, l-chloro-3,3-dimethylpentane is formed by isomerization of the primary product to give fcrf-amyl chloride, which adds to ethylene more readily than do starting propyl halides (Scheme 5.4). The same product is also obtained54 when ethylene reacts with neopentyl chloride in the presence of AICI3. 

Recent experimental studies have indicated that a- or p-substitution may alter the gas-phase substitution reactions in different ways than in solution. Kebarle has determined that the activation barrier for the gas-phase reaction of chloride with alkyl bromides increases as Me (-1.9 kcal mol" ) < Et (-1.3 kcal mol" ) < -Bu (0.0 kcal mol" ) < i-Pr (5.6 kcal mol" ). While a-branching does increase the barrier for the substitution reaction, p-branching appears to lower the barrier. This is even more apparent in the essentially equivalent rates for the reaction of fluoride with ethyl and neopentyl chlorides in the gas phase. Another example is the unexpectedly small difference (1.9 kcal mol" ) in the activation energies for the reactions of chloride with methyl- and ferf-butyl chlororoacetonitriles, which was subsequently expanded to include the ethyl and (-propyl analogs (Table 6A) ... 

Some primary and other alkyl halides with special structural features pose problems. With increasing chain length ease of reaction decreases . Neopentyl chloride is difficult to transform to its organomagnesium-halide reagent, even in THF The best method for the neopentyl reagent is from the bromide in THF ... 

Oxidative addition can also occur between anionic metal complexes and alkyl electrophiles. In this case, the halide becomes a byproduct, rather than a ligand, in the final metal complex. One well-studied example of oxidative addition to an anionic metal complex by an Sj 2 pathway involves the "supernucleophile" Fe(CO) ". This complex reacts rapidly with most organic halides, including hindered halides containing strong C-X bonds, such as neopentyl chloride. The products from multistep reactions of this complex are consistent with 100% inversion in the oxidative addition step. This and the other evidence in Figure 7.1 support reaction by a classic S 2 pathway. 

Neopentyl chloride, CH3C(CH3)2CH2C1, is a primary alkyl halide that undergoes Sj.j2 reactions at extremely slow rates. Offer an explanation for this fact that is consistent with the mechanism for this reaction. Draw a suitable illustration of the transition state for the rate-determining step as part of your... 

The new zirconium hydride-alkyls, CpaZr(H)R, have been obtained by reduction of corresponding chlorides. They eliminate RH (R=cyclohexylmethyl, cyclohexyl, ethyl, octyl, or neopentyl) under hydrogenation in a reaction which has been demonstrated by labelling studies to involve initial co-ordination of dihydrogen (Scheme The starting chlorides react with CO rapidly at 0 °C... 

Cooper(I) carboxylates give esters with primary (including neopentyl without rearrangement), secondary, and tertiary alkyl, allylic, and vinylic halides. A simple Sn mechanism is obviously precluded in this case. Vinylic halides can be converted to vinylic acetates by treatment with sodium acetate if palladium(II) chloride is present. ... 

The alkyl halides that react by the S l mechanism have a relatively low reactivity toward polar nucleophilic substitution due to steric, electronic or strain factors11, as shown for several bicycloalkyl, cycloalkyl and neopentyl halides and for /-butyl chloride. In the following section the reaction of these alkyl halides with different nucleophiles will be discussed. 

Cavell also reported alkyl derivatives. Tetrabenzyl zirconium was found to react separately with one molar equivalent of two parent methanes to afford complexes 135 and 136 in excellent yields.66 The 13C NMR chemical shifts of the methandiide centres in 135 (Ad = adamantyl) and 136 of 82.8 and 84.4 ppm are clearly different from the dichloride congeners and reflect the substitution of the chlorides by alkyls. The corresponding hafnium dialkyl 137 was also prepared from 133 and neopentyl lithium and the methanide resonance for this complex appeared at 71.6 ppm in its 13C NMR spectrum.63 Noteably, these alkyls displayed far greater stability than their homoleptic tetraalkyl cousins. 

Representative reductions of alkyl halides with LiBEtyH are shown in Table 4. Most alkyl halides, including chlorides, are reduced under mild conditions in essentially quantitative yields. Even hindered alkyl halides, such as neopentyl bromide and cAro-norbomyl bromide, undergo facile reduction to the corresponding alkanes in more than 96% yield with this reagent. 

A general method fen the synthesis of alkyl iodides is the reaction of tosylates or methanesulfonates with sodium iodide in acetone or magnesium iodide in diethyl ether (equation 30). The reaction is not always a clean Sn2 process. Stereoselectively deuterated neopentyl tosylate, for example, gives with Nal in HMPA only low yields (34%) of the racemic iodide (equation 31). This is in contrast to analogous reactions with bromide and chloride (see Sections 1.7.3.2 and 1.7.2.2), where better yields with complete inversion are observed. 

Alkyl cyanates. Kauer and Henderson found that an alcohol such as neopentyl alcohol can be converted into the corresponding cyanate, if in low yield, by successive treatment with sodium hydride and cyanogen chloride. 1,4-Dihydroxybicyclo-[2.2.2]octane afforded the dicyanate, m.p. 155-156 , in reasonable yield. The... 

Displacements. Primary and secondary alkyl chlorides react rapidly and exother-mally with sodium cyanide in partial solution in dimethyl sulfoxide to give the corresponding nitriles in excellent yield. - The reactions are faster and the yields better than in the reactions of the corresponding bromides or iodides in aqueous alcohol. Neopentyl and neophyl halides can be converted by this method to... 

Lower alkyl iodides are obtained by treating the p-toluenesulfonates with concentrated aqueous potassium iodide (0.2 mole of KI in 10 ml of water) and are distilled off through a column continuously during the reaction. The aryl ester does not react with Nal in acetone. Although neopentyl iodide can be obtained from the p-toluenesulfonate and Nal,986 it is recommended987 that neopentyl bromide (86% yield) and chloride (60% yield) should be prepared by way of triethylneopentyloxysilane ... 

Alkyl chlorides.Alcohols react with hydrogen chloride in HMPT at 50-85° to form alkyl chlorides in 65-90% yield. The reaction of primary alcohols is rapid (30 min.) longer reaction times are required for secondary and tertiary alcohols (about 1 hr.). Neopentyl alcohol reacts without formation of rearranged products. Racemic product was obtained from 2-octanol. 

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