Synthesis and free radical ring‐opening polymerization of 2‐methylene‐4‐phenyl‐1,3‐dioxolane

The cyclic ketene acetal, 2‐methylene‐4‐phenyl‐1,3‐dioxolane ( 3 ), was shown to undergo free radical ring‐opening polymerization to produce the polyester, poly[γ‐(β‐phenyl)butyrolactone]. The monomer 3 was synthesized by an acetal exchange reaction of chloroacetaldehyde dimethyl acetal with styrene glycol in an 87% yield followed by dehydrochlorination of the resulting cis and trans ‐2‐chloromethyl‐4‐phenyl‐1,3‐dioxolane ( 2 ) with potassium tert ‐butoxide in tert ‐butyl alcohol in a 70% yield. 3 was shown to undergo essentially quantitative free radical ring‐opening at all temperatures from 60–150°C and also nearly complete regioselective ring‐opening with cleavage to give the more highly stable secondary benzyl free radical. Even in free radical copolymerization with styrene, methyl methacrylate, vinyl acetate, or 4‐vinylpyridine, 3 gives essentially complete ring opening to introduce an ester groups into the backbone of the addition copolymer. The structures of the polymers were established by elemental analysis and 1 H and 13 C NMR spectroscopy.