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Cross-Linking of Brominated Poly(isobutylene-co-isoprene) by N-Alkylation of the Amidine Bases DBU and DBN
journal contribution
posted on 2005-05-31, 00:00 authored by Ralph A. Whitney, Anca Penciu, J. Scott Parent, Rui Resendes, William HopkinsAn unusual cross-linking of brominated poly(isobutylene-co-isoprene), BIIR, has been shown
to occur in the presence of the normally nonnucleophilic amidine bases 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1,5-diazabicyclo[4.3.0]non-5-ene (DBN). Model compound studies using brominated
2,2,4,8,8-pentamethyl-4-nonene (BPMN) have provided structural information which indicates that this
cross-linking most likely occurs through a sequence of reactions which involves the following: (1)
N-alkylation of the amidine base to an amidinium salt, (2) hydrolysis of the salt to an ammonium lactam,
(3) deprotonation of the ammonium lactam to an amino-lactam, and (4) a second amine N-alkylation.
The ability of DBU and DBN to undergo N-alkylation with BIIR has been confirmed by reaction of BIIR
in solution with an excess of each of these bases to give N-alkylation products that have been characterized
spectroscopically.