Azetidinium ions

Substitution of proton on the nitrogen with alkyl group, as in the case of aziridines, simplifies the mechanism of polymerization. In the polymerization of 1-methylazetidine, termination due to the chain transfer to polymers is still detectable [176], Further substitution at carbon atoms reduces the extent of chain transfer to polymer and in the cationic polymerization of 1,3,3-trimethylazetidine the concentration of active species, quaternary azetidinium ions ... 

Cyanoazetidines and azetidinium ions Scaffolds for molecular diversity 13EJO2045. 

The regiospecific 5 2 ring-opening reactions of 2-substituted aziridinium and azeti-dinium ions at the least-substituted carbon by 4-dimethylaminopyridine in acetonitrile occurs 17000 times faster with the aziridinium ion than with the azetidinium ion. However, only a portion of the faster rate is due to the additional ring strain in the aziridinium ion. A/7 =46.5kJ mor and A5 = 165.4 J mor K" for the aziridinium ion reaction. 

The less reactive, weak electrophilic azetidinium ions undergo ring-opening reactions with charged nucleophiles such as carboxyl ions. The reaction of PTHF with thiolane gives similar results (307). 

Further reaction of the quaternary azetidinium ion with any amine leads to a tertiary amine. Another route to a tertiary amine group is attack of a secondary amine in a polymer chain on an azetidinium ion. Finally, a polymer containing 20% primary, 20% tertiary, and 60% secondary amino functions is formed. 

The regiospecificity of the ring-opening 5 2 reactions of several azetidinium ions with a quaternary a-carbon to the nitrogen has been determined using an excellent (N3 ), a... 

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