Living coupling reaction in living cationic polymerization. 3. Coupling reaction of living polyisobutylene using bis(furanyl) derivatives

Citation
S. Hadjikyriacou et R. Faust, Living coupling reaction in living cationic polymerization. 3. Coupling reaction of living polyisobutylene using bis(furanyl) derivatives, MACROMOLEC, 33(3), 2000, pp. 730-733
Citations number
9
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
MACROMOLECULES
ISSN journal
00249297 → ACNP
Volume
33
Issue
3
Year of publication
2000
Pages
730 - 733
Database
ISI
SICI code
0024-9297(20000208)33:3<730:LCRILC>2.0.ZU;2-Q
Abstract
Living coupling reactions of living polyisobutylene (PIB) with bis(furanyl) compounds, 2,2-difurylmethane (DFM), 2,5-bis(2-furylmethyl)furan (bFMF), 2 ,2-difurylpropane (DFP), and 2,5-bis(2-furyl-2-propyl)furan (bFPF) were inv estigated in the presence of TiCl4 as Lewis acid in hexanes/CH3Cl 60/40 and 40/60 (v/v) at -80 degrees C and with bFPF in conjunction with BCl3 in CH3 Cl at -40 degrees C. The products obtained with DFM and bFMF were slightly colored most probably due to alpha-hydride abstraction and the development of conjugated structures. DFP and bFPF, lacking alpha-hydrogens, yielded co lorless products. In hexanes/CH3Cl 60/40 (v/v), coupling was very slow and incomplete after 2 h with DFM and DFP, which was ascribed to deactivation o f the second furanyl ring after monoaddition. Coupling was faster with bFMF ; however, the coupling efficiency was only 85% after 2 h due to some side reactions that consumed bFMF. Coupling was rapid and quantitative with bFPF in the presence of TiCl4 in hexanes/CH3Cl 60/40 (v/v) at -80 degrees C. In creasing the solvent polarity to hexanes/CH3Cl 40/60 (v/v) further increase d the late by 2-fold. Efficient, albeit slow, coupling was also achieved wi th bFPF in CH3Cl at -40 degrees C in the presence of BCl3. The mechanism of the coupling reaction was investigated in the presence of TiCl4 in hexanes /CH3Cl 60/40 (v/v) at -80 degrees C by quenching the reaction mixture with tributyltin hydride after complete coupling had been achieved. Identificati on of the product structure by H-1 NMR spectroscopy verified the formation of stable dications upon coupling and confirmed that this reaction is a liv ing coupling reaction.