Diels-Alder reactions of 5-[methoxypoly(oxyethylene)]-(3E)-1,3-pentadiene (1a) with maleic anhydride, diethyl acetylenedicarboxylate (DADC), and acrolein were investigated for the synthesis of new poly(ethylene glycol) derivatives. To facilitate the characterization of the derivatives, Diels-Alder reactions of 5-methoxyethoxy-(3E)-1,3-pentadiene (1b) with the aforementioned dienophiles were also studied. The reaction of o-toluidine with the cycloaddition product from maleic anhydride and 1b resulted in the corresponding amide products. The reactions of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with cycloadducts derived from 1a and 1b with DADC resulted in the aromatization of the corresponding products. An NMR analysis of the adducts obtained from la and acrolein in water and from 1b and acrolein in water./acetonitrile (4:1 v/v) indicated a mixture of endo and exo, with the endo concentration being approximately 80%. (c) 2005 Wiley Periodicals, Inc.