Synthesis of Heterocyclic Quinones Containing Bridgehead Nitrogen Atom from 2-Aminonaphtho[2,3-d]thiazole-4,9-dione.

Abstract

Imidazonaphthothiazole derivatives III-VI were prepared by treatment of I with phencyl bromide, chloroacetic acid, diethyl oxalate and 2,3-dichloroquinoxaline respectively. The reaction of I with ethyl acrylate, ethyl acetoacetate and diethyl malonate gave the corresponding naphthothiazolopyrimidine derivatives VIII-XI.Imidazo[2,l-b]thiazole and its derivatives are useful heterocycles for pharmacological* " 5) . Therefore a number of methods has been developed for the preparation of these derivatives' 1 ' 3,6 '^. Quinones are also reported to have a wide variety of biological activities' 8 ' 10) . In extension of our work on the synthesis of nitrogen heterocyclic quinones' 11,12) , we report here the synthesis of fused imidazothiazolo and thiazolopyrimidinoquinone ring system and evaluation of their biological activities have been undertaken.Thus, 2,3-dichloro-l,4-naphthoquinones reacted with thiourea to give 2-aminonaphtho[2,3-d]thiazole-4,5-dione li 3) . Treatment of I with phencyl bromide following the method of Saldabols et al' 14) , yielded the 2-imino-3-benzoylmethylnaphtho[2,3-d]thiazole-4,9dione hydrobromide II as a cyclic intermediate product, which on heating in absolute ethanol underwent cyclization giving 2-phenylimidazo[2 ,1 -b]naphtho[2,3-d]thiazole-5,10-dione III [Scheme 1]. Compound III was also obtained directly by refluxing I with phencyl bromide in absolute ethanol. The reaction of I with chloroacetic acid afforded 2-hydroxyimidazo[2 ,1 -b]naphtho[2,3-d]thiazole-5,10-dione IV. On the other hand, refluxing of I with diethyl oxalate [Scheme 1] in absolute ethanol gave 2,3-dihydroimidazo[2 ,1-b]naphtho[2,3-d]thiazole-2,3,5,10-tetrone V in good yield. Compound I when refluxed with 2,3-dichloroquinoxaline in absolute ethanol gave quinoxalino[2,3:4,5 ]imidazo[2 ,1 -b]naphtho[2,3-d]thiazole-8,13-dione VI [Scheme 1], The structures of Π-VI were confirmed based on its correct microanalytical results and spectral data [cf. Table 2], 585 Brought to you by |