To a mixture of 2-[(thiophen-2-ylmethyl)-amino]-thiazol-4-one (34.0 mg, 0.16 mmol, (prepared as described below), AcONa (160 mg, 1.95 mmol), and 6-formyl-4-isopropoxy-[1,5]naphthyridine-3-carbonitrile (57.9 mg, 0.24 mmol) (see Example 1) in a sealed tube was added AcOH (0.3 mL). The reaction mixture was heated to 80° C. (oil bath) for 5 hrs. The reaction mixture was then cooled to r.t. and triturated with water. The solid was collected by filtration and washed with water. The solid was then suspended in AcOEt (20 mL) and filtered. The solid was washed with AcOEt and dried to give 4-isopropoxy-6-{4-oxo-2-[(thiophen-2-ylmethyl)-amino]-4H-thiazol-5-ylidenemethyl}-[1,5]naphthyridine-3-carbonitrile as a light brown solid (35.4 mg, 50.8%). HR-ES (+) m/e calcd for C21H17N5O2S2 (M+H)+ 436.0897. found 436.0895.
