New Poly(oxyethylene) Derivatives from Diels–Alder Reactions of 3‐[Methoxypoly(oxyethylene)]methylene Furan

Summary: A new poly(ethylene glycol) derivative, 3‐[methoxypoly(oxyethylene)]methylene furan, I , was prepared from the reaction of 3‐furanmethanol with the mesylate of methoxypoly(oxyethylene) in tetrahydrofuran. The degree of end‐group conversion, as determined by NMR spectroscopy, was 100%. The Diels–Alder reactions of I with N ‐phenylmaleimide, N ‐glycinylmaleimide, maleic anhydride, N , N ′‐hexamethylene bismaleimide, and diethyl acetylenedicarboxylate resulted in the corresponding adducts. For the adduct derived from I and N ‐phenylmaleimide, its thermal reversible character was confirmed by applying a retro‐Diels–Alder reaction in the presence of a large excess of 2‐methylfuran, which restored the initial polymer I quantitatively. The adduct obtained from I and N ‐glycinylmaleimide was converted into its succinimidyl ester and its hydrolysis rate in phosphate buffer (pH = 8) was determined. The reactivity of the adduct derived from I and N , N ′‐hexamethylene bismaleimide with benzyl mercaptan was also investigated.