Synthesis and Some Pigment Properties of 7, 15-Dihydropyrido[2, 1-b] PYrido[1', 2': 1, 2]pyrimido [4, 5-g]quinazoline-7, 15-dionet

Abstract

7, 15-Dihydropyrido[2, 1-b]pyrido[1', 2': 1, 2]pyrimido[4, 5-g]quinazoline--7, 15-dione [ 2] was efficiently prepared by the dehydrogenation of 6, 7, 14, 15-tetrahydropyrido[2, 1-b]pyrido[1', 2': 1, 2]pyrimido[4, 5-g]quinazoline-7, 15-dione [ 4], which was derived from diethyl 2, 5-dioxocyclohexane-1, 4-dicarboxylate and 2-aminopyridine, with a nitro compound in the presence of alkali. The reaction is considered to be accompanied by the hydrolysis to give 2, 5-bis (2- pyridylamino)terephthalic acid [5] followed by cyclization. p-Benzoquinone also dehydrogenated [4] to give [2] directly under acidic conditions. The reaction of chloranil with [ 4 ] afforded the molecular complex of [ 2 ] with tetrachloro-p-hydro- quinone, from which [ 2 ] was extracted with conc. FI2SO₄. Some pigment properties of [2], such as color, the resistance to light, heat, acid, alkali, and organic solvents were also examined in comparison with those of quinacridone and/or cadmium red. From these results, it is concluded that the pigment is quite similar to cadmium red in color and has excellent pigment properties as a substitute for cadmium red. t Studies on Quinazoline Pigments. I.