Selective dealkylation of aromatic alkoxylated compounds

Selective de-ethylation of 2-ethoxyanisole is observed using KOtBu as the reagent in the presence of 18-crown-6 as the phase transfer agent (PTA). With the addition of ethylene glycol (E.G.), the selectivity is reversed and demethylation occurs (Eq. (33) and Tab. 3.13). If the involvement of microwaves is favorable in both examples, the second reaction should be more strongly accelerated than the first [87]. 

The microwave-specific effect is more apparent in the case of demethylation (Sn2). The microwave acceleration clearly is more pronounced with the difficulty of the reaction, thus constituting a clear example of an increased microwave effect with a more difficult reaction, indicative of a later TS position along the reaction coordinate. The microwave effect may also be connected to the more localized charge in the Sn2 transition state (three centers) when compared to that of p-E2 (charge developed over five centers). 

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