Synthesis and Reactions of Some Substituted Heterocyclic Systems as Anti-arrhythmic Agents

A series of substituted heterocyclic systems were prepared from N ¹-[4-(2-thienylmethylene)phenyl]-5-chloro-2-methoxybenzamide, which was prepared from the corresponding 5-chloroanisic acid (2-methoxy-4-chlorobenzoic acid) as starting material. Condensation of the thienylmethylene derivative with guanidine hydrochloride, urea, or thiourea afforded the aminopyrimidine, pyrimidinone, and thioxopyrimidine derivatives. The latter was condensed with chloroacetic acid to yield a thiazolopyrimidine, which was condensed with 2-thiophenealdehyde to yield the arylmethylene derivative, however, it was also prepared directly from thiopyrimidine by the action of chloroacetic acid, 2-thiophenealdehyde, and anhydrous sodium acetate. Treating of the thienylmethylene derivative with phenylhydrazine or hydrazine hydrate in dioxane afforded N-phenylpyrazoline and a pyrazoline, which was reacted with acetyl chloride in dioxane affording the N-acetyl analogue. The thienylmethylene derivative was reacted with malononitrile or ethyl cyanoacetate in the presence of ammonium acetate to yield the corresponding cyanoaminopyridine and cyanopyrimidone derivatives. Also, it was reacted with hydroxylamine hydrochloride in pyridine to give the oxime derivative, which was cyclized with acetic anhydride. On the other hand, condensation of the thienylmethylene derivative with ethyl cyanoacetate in the presence of sodium ethoxide or cyanothioacetamide gave the cyanopyrane and pyridine thione derivative, which was treated with ethyl chloroacetate affording the ethyl carboxylate derivative. The pharmacological screening showed that many of these compounds have good anti-arrhythmic activity and low toxicity.