1: 2-carboxy-4-nitro-chlorobenzene With thionyl chloride; N,N-dimethyl-formamide in toluene 1.5 h; Heating / reflux; 2: potassium tert-butylate in tetrahydrofuran T=0°C; 0.5 h;

thionyl chloride in tetrahydrofuran; 1,2-dichloro-ethane; N,N-dimethyl-formamide

sulfuric acid in dichloromethane T=20°C; Esterification; 48 h;

in N,N-dimethyl-formamide Yield given;