Hydroxyalkylation acetophenone

As with the previous reported conclusion concerning the polymeric photoinitiators based on hydroxyalkyl acetophenone moiety (KIP), in this case rm (Eq. 4) also is much higher in the polymeric systems than in the models (Table 22), indicating that the B radicals anchored to the polymer backbone are less prone to give radical-radical combination, thus favouring flieir reaction with the acrylic monomers. 

Like the piperidones, a wide variety of TV-heterocyclic aromatic compounds show an ability to activate electrophilic functional groups. It is known that acetophenone is completely protonated in CF3SO3H, however in the presence of benzene there is no hydroxyalkylation (condensation) reaction.12 On the other... 

Diprotonated, superelectrophilic intermediates were suggested to be involved in both conversions. Considering protonated aldehydes, benzal-dehyde gives a carboxonium ion that is significantly resonance stabilized and thus unreactive towards aromatic substrates such as o-dichlorobenzene or nitrobenzene. Pyridinecarboxaldehydes, however, show much higher electrophilic reactivities due to their ability to form via TV-protonation the superelectrophile (5, eq 8).10 A similar situation is seen in the hydroxyalkylation reactions of acetyl-substituted arenes. Acetophenone is fully protonated in excess triflic acid, but the resulting carboxonium ion (6) is... 

Cyclic ketals of acetophenone can be prepared directly under basic conditions by the reaction of aryl triflates, bromides or iodides with hydroxyalkyl vinyl ethers in the presence of a catalytic amount of palladium(II) acetate and 1,3-bis(diphenylphosphino)propane (DPPP). The example illustrated in Scheme 2.39 is noteworthy since a protected methyl ketone was appended to an arene in the presence of a reactive aldehyde functionality. 

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