Reactivity of alkyl groups

It is well known that in nitrogen-containing heterocyclic compounds the reactivity of alkyl groups is enhanced. In the thiazole series, alkyl groups in the 2-position are reactive towards carbonyl compounds and condensations may be realized. 

Disproportionation (transalkylation) and positional isomerization usually take place simultaneously when either linear or branched alkylbenzenes are treated with conventional Friedel-Crafts catalysts or with Nafion-H. The reactivity of alkyl groups to participate in transalkylation increases in the order ethyl, propyl < isopropyl < tert-butyl.117 207 217... 

The reactivity of alkyl groups on five-membered rings with one heteroatom is similar to that of alkyl groups on benzenoid rings. Because of the high reactivity of the heterocyclic nuclei, specific reactions... 

Not only trialkyltin halides, but also tetraalkyltins themselves act in this way as perturbers . Evidence for this effect was obtained47 by determination of the relative reactivities of alkyl groups in unsymmetrical tetraalkyltins. The following data are typical. 

Zaera F (1992) Preparation and reactivity of alkyl groups adsorbed on metal surfaces. Acc Chem Res 25 260... 

Alkyl-alkyl cross-coupling reactions have historically been the most difficult to realize. Among the many obstacles to the effective development of such a system are the lower reactivity of alkyl groups relative to alkenyl and aryl groups, as well as side processes such as -hydride elimination that are accessible with alkyl substrates. More reports by Fu et al. have disclosed successful alkyl cross-coupling protocols... 

It is an important findings that the rate of propagation varied depending on the degree of polymerization, l.e., kp-> kp2>kp. .=kp (ni3). These values were successfully determined since i and Pn (nk2) were directly observed by nmr spectroscopy. The difference in kp is due to different electrophilic reactivity of alkyl groups toward BCMO monomer when n"l,... 

The use of zinc chloride and related substances, or acetic anhydride, is a common feature of many reactions of alkylpyridines. The first type of reagent probably exercises a generalized acid catalysis, augmenting the reactivity of alkyl groups by coordination with the nitrogen atom. Acetic anhydride... 

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