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Synthesis of rhodamine-bromomaleimides. a) (COCl)2, 20 °C, 15 h; b) piperidin-4-yl carbamic acid tert-butyl ester (10.4 equiv), CsCO3 (10.4 equiv), CH2Cl2, 20 °C, 24 h, 71 % (2 steps); c) TFA/CH2Cl2 (1:1), 20 °C, 5 h, 100 %; d) maleic anhydride (1.4 equiv), AcOH, 120 °C, 5 h, 40 %; e) bromomaleic anhydride (1.4 equiv), AcOH, 120 °C, 5 h, 66 %; f) dibromomaleic anhydride (1.4 equiv), AcOH, 120 °C, 5 h, 66 %.
