3-Dicyanomethylene-2,4-dibutyl-squarate 、 potassium 1-(5'-carboxypentyl)-2,3,3-trimethylindolenium bromide-5-sulfonate 以
甲苯 、
正丁醇 为溶剂,
反应 4.0h,
以32%的产率得到2,4-bis[N-(ε-butoxycarbonylpentyl)-3,3-dimethyl-5-sulfo-2-indolinylidene methyl]cyclobutenediylium-3-dicyanomethylene-1-oxolate