Substrates, ambident, allylic

Some substrates (e.g., 1,3-dichlorobutane) can be attacked at two or more positions. We may call these ambident substrates. In the example given, there happen to be two leaving groups in the molecule, but there are two kinds of substrates that are inherently ambident (unless symmetrical). One of these, the allylic type, has already been discussed (p. 327). The other is the epoxy (or the similar aziridine or episulflde) substrate.437... 

A common problem in the manufacture of fine chemicals is that a substrate may have more than one reactive site. A well known, but intractable, problem is the nitration of monosubstituted benzenes, which always leads to a mixture of isomers. Reactions which involve nucleophilic substitution are more amenable to control of regioselectivity by choice of solvent. An excellent review on the reactivity of ambident anions is available, in which this subject is treated [17]. An instructive example is the alkylation of phenol with allyl chloride [18] (equation 12.10). Table 12.13 shows how the properties of O- and C-alkylation are affected by solvent. 

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