Step B: Synthesis of ethyl 4-hydroxy-8-methoxyquinoline-3-carboxylate: Diethyl 2-(((2-methoxyphenyl)amino)methylene)malonate (47.6 g, 162 mmol) was suspended in Dowtherm (100 mL) and heated to 250 °C. The reaction mixture was kept in a sand bath overnight, subsequently cooled to room temperature and diluted with pentane (750 mL). The resulting solid product was collected by filtration and washed with hexane to afford the target compound (25.7 g, 64% yield). Mass spectrometry analysis (APCI) showed m/z 248.0 ([M + H]+).
