Reacts at the 2-position with isocyanates in the presence of base to give 2-aminofuranone derivatives via a ketene N-acetal intermediate: Chem. Ber., 109, 212 (1976). Isothiocyanates similarly give 2-aminothiophenones: J. Chem. Soc., Perkin 1, 1078 (1981). Acid-catalyzed reaction with phenols gives 3-(chloromethyl)coumarins, readily convertible to benzofuran-3-acetic acids: Heterocycles, 41, 647 (1995).