Electrophilic Olefins Containing Anionic Leaving Groups as New Cationic Initiators

Abstract

Five tri-and tetra-substituted electron-poor olefins $\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\thicksim}$}}\to {1} - \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\thicksim}$}}\to {5}$ containing β-anionic leaving groups initiated cationic polymerization of p-methoxystyrene with widely varying rates. Compounds $\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\thicksim}$}}\to {1}$ and $\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\thicksim}$}}\to {2}$ were highly active organic initiators. The yields and molecular weights of the polymers decreased with decreasing electron deficiency of the initiator through the series. The same was true when the excellent leaving group trifluoromethanesulfonate was replaced by the poorer leaving group chloride. Substituted butadienes were isolated along with homopolymer from the reaction of p-methoxy-styrene with compounds $\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\thicksim}$}}\to {3}$ and $\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\thicksim}$}}\to {4}$. In ring opening polymerization, compound $\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\thicksim}$}}\to {1}$ polymerized THF and trioxane with reactivity comparable to that of methyl trifluoromethanesulfonate. The mechanism of pol3nnerization was suggested to go through the formation of charge transfer complexes and 1, 4-tetramethylenes (1, 4-zwitterions) which propagate p-methoxystyrene cationic polymerization with the leaving group anion as gegen ion.