The effect of the substituent on the palladium(II)-catalyzed addition polymerization of
functionalized norbornene derivatives was examined. Endo-substituted norbornenes are
polymerized more slowly than their corresponding exo isomers. The size of the substituent
plays a role. However, the coordinating ability of the functionality plays an even bigger role
in attenuating polymerization than its size. The formation of chelates upon the coordination
of the endo-functionalized norbornene is responsible, in part, for the observed decrease in
polymerization rate. A further, and even greater, reason for the diminution of activity of
both the endo- and the exo-functionalized isomers is simply the coordination of the
functionality to the metal center.
Dedicated to Professor Giambattista Consiglio on the occasion of his 65th birthdayThe reaction of N-alkylbenzaldimines with carbon monoxide (CO) in the presence of cobalt (Co) catalysts resulted in the formation of N-alkylphthalimidines ( Table 1). Their formation is proposed to occur by CÀH activation of the aryl ring, migratory insertion of the hydride species into the benzaldimine functionality, CO coordination, and insertion into the CoÀC bond, followed by reductive elimination of the N-alkylphthalimidine and regeneration of the starting Co species (Scheme 4). Deuterium ( 2 H)-labeling NMR studies are consistent with this mechanism (Scheme 5).
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