Addition reactions of polymers containing pendant cyclic iminoethers with thiols, carboxylic, thiocarboxylic and sulfinic acids

Abstract

AbstractPoly[1‐(2‐oxazoline‐2‐yl)ethylene] (2a), poly[1‐(5‐methyl‐2‐oxazoline‐2‐yl)ethylene] (2b), poly[1‐(4,4‐dimethyl‐2‐oxazoline‐2‐yl)ethylene] (2c), poly[1‐(4,4‐dimethyl‐5,6‐dihydro‐4H‐1,3‐oxazine‐2‐yl)ethylene] (2d), and poly[1‐(4,4,6‐trimethyl‐5,6‐dihydro‐4H‐1,3‐oxazine‐2‐yl)ethylene] (2e) were synthesized with high yields by radical polymerization, using AIBN as initiator. Polymer 2a was found to be soluble in water and in organic solvents such as methanol, acetone, chloroform and benzene, polymer 2b in hot water and in the same organic solvents, and polymers 2c and 2d are insoluble in cold and hot water. However, polymers 2d and 2e are soluble in diethyl ether and hexane. Addition reactions of polymers 2a–e with carboxylic acids and thiols were investigated. Reactions of polymer 2a with acetic acid, benzoic acid and cinnamic acid at 110°C for 10 h proceeded with 57–74 mol‐% conversion in DMF, NMP and DMSO, and reactions with benzenethiol and thiobenzoic acid quantitatively under the same reactions conditions. Reactions of polymers 2b and 2c with carboxylic acids proceeded with 4–36 mol‐% conversion, and with benzenethiol and thiobenzoic acid with 80–96 mol‐% conversion. From the results the following order of reactivities of these polymers may be suggested: 2a ≃ 2d > 2e > 2b > 2c. According to their higher nucleophilicity, the reactivities of benzenethiol and thiobenzoic acid towards the pendant 2‐oxazoline ring are much higher than those of carboxylic acids.