1: acetonitrile With n-butyllithium in tetrahydrofuran; hexane T=-78°C; Metallation; 0.333333 h; 2: 2-(dimethylamino-methyleneamino)-5-ethoxy-4-methoxy-benzoic acid methyl ester in tetrahydrofuran; hexane T=-78°C; Addition; 1 h; 3: With acetic acid in tetrahydrofuran; hexane T=-78 - 25°C; Cyclization; Further stages.;