Synthesis of naphtho[2',3':4,5]imidazo[2,1-<Emphasis Type="Italic">b</Emphasis>][1,3]-thiazole-5,10-dione and naphtho[2',3':4,5]imidazo-[2,1-<Emphasis Type="Italic">b</Emphasis>][1,3]benzothiazole-7,12-dione

The reaction of 2,3-dibromo-1,4-naphthoquinone with 2-aminothiazole in MeONa/MeOH at 60oC for 3 h gave naphtho2',3':4,5]imidazo2,1-b]1,3]thiazole-5,10-dione in 64% yield. The reaction of 2,3-dibromo-1,4-naphthoquinone with 2-aminobenzothiazole under the above-mentioned conditions gave 2-(benzod]thiazol-2-ylamino)-3-bromonaphthalene-1,4-dione in 64% yield, which on treatment with Na/THF or NaN₃/acetone under reflux conditions gave naphtho2',3':4,5]imidazo2,1-b]1,3]- benzothiazole-7,12-dione in 69 and 56% yields, respectively.