Anomalous Ring-Opening Reaction of 4-Styrylcoumarin Dimer with Amines
Hirohiko MIURA, Katsunori TANAKA, Kiyoshi SAITO, Tomonori TAKATA and Masaki HASEGAWA*
Department of Functional Chemistry and Technology, Faculty of Engineering, Toin University of Yokohama; 1614 Kurogane-cho, Aoba-ku, Yokohama-shi 225-8502 Japan
Coumarin dimers generally show high reactivity in ring-opening polyaddition reaction with diamine to give a high-molecular-weight polyamide. However, the reaction of anti head-to-tail 4-styrylcoumarin dimer with hexamethylenediamine gave no polyamide at all. It was found that after the first ring-opening reaction by amine, styryl group on cyclobutane ring unexpectedly decreased electrophilicity of carbonyl group and disturbed the second ring opening reaction. After the first ring-opening, IR peaks of carbonyl group in the lactone ring and olefin group in the styryl group, remarkably shifted to the lower wavenumber. Based on the observed IR spectral shifts, unusual stabilization of the second lactone ring was shown.
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