Reactivity of Cyclic Imino Ether Salts Having Vinyl Group V. Spontaneous and Base-Catalyzed Polymerization of N-Protio Salts of 2-Alkenyl-2-oxazolines and 2-Alkenyl-5,6-dihydro-4H-1,3-oxazines

Abstract

ABSTRACT:Four derivatives of 2-alkenyl cyclic imino ethers were reacted with fluorosulfonic and with trifluoromethanesulfonic acids. 2-Isopropenyl-2-oxazoline (lb) and 2-isopropenyl-5,6-dihydro-4H-l,3-oxazine (Id) formed the stable N-protonated salts at 0°C. Whereas, 2-vinyl-2-oxazoline (la) and 2-vinyl-5,6-dihydro-4H-l,3-oxazine (le) were polymerized on protonation (spontaneous polymerization) at the same temperature to give polymers consisting of two kinds of units; one was formed by the opening of vinyl group and the other was derived by a proton transfer. By a low temperature reaction of la with fluorosulfonic acid at -20°C, the N-protonated salt was successfully isolated, but the corresponding salt of le was not obtained by the same procedure. For these three salts isolated, base-catalyzed polymerization was examined with pyridine and triethylamine as initiators at a temperature below 20°C. The salt of lb gave a polymer consisting exclusively of the proton transferred unit. On the contrary, the salt of Id was not polymerized at all. As a reference salt, the N-methyl salt of Id, i.e., 3-methyl-2-isopropenyl-5,6-dihydro-4H-l,3-oxazinium salt, was prepared by the reaction of Id with methyl trifluoromethanesulfonate, which was not polymerized, too. On the basis of these findings the reactivity of N-methyl and N-protio salts of 2-alkenyl cyclic imino ethers were discussed.

Chemistry and technology of 2‐alkenyl azlactones

“…Similar acid‐catalyzed reactions, although with excess or stoichiometric quantities of strong acids, had been reported with analogous 2‐alkenyl oxazolines to form Structures 1 and 2. With 2‐isopropenyl oxazoline the poly(Michael addition) Structure 1 was identified,17 whereas 2‐vinyl oxazoline provided a structure containing a combination of poly(Michael addition) ( x units in 2, predominating) and carbon–carbon catenated structures ( y units) 18 …”

Poly(2-isopropenyl-2-oxazoline) as a Versatile Functional Polymer for Biomedical Applications

“…Cationic polymerization of IPOx initiated by HClO 4 is very sensitive to the presence of free radicals [28]. The linear polymer was only obtained in the case when polymerization was carried out in the presence of hydroquinone at temperatures ranging from 70 to 125 • C. On the other hand, Saegusa et al reported an interesting ring-preserved polymerization using N-protio-2-isopropenyl-2-oxazolinium salt, which has a close similarity to N-methyl salt [58].…”