Figure 4.5 DMC as an ambident nucleophile.
step consists of a hard-hard reaction, and selectively produces a soft anion, which, in the second phase, selectively transforms into the final monomethylated product, via a soft-soft nucleophilic displacement (yield >99% at complete conversion, using DMC as solvent) (Fig. 4.5).
The combination of the dual electrophilic character of DMC with its reaction products allows two consecutive steps to occur in a selective way for what concerns both reaction sequence and yields: first, the hard-hard reaction occurs and produces a soft anion only; and second, a soft-soft nucleophilic displacement leads to the final product. Since hard-soft and soft-hard interactions are inhibited, double methylation and double carboxymethylation do not occur.
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