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Syntheses of the 1 -, 2-, and 4-thiosemicarbazones and the 1and 4-amidinohydrazones of Z-hydroxy-l,4-naphthoquinone (I) are described. The position of condensation of the quinone (I) with thiosemicarbazide is pH dependent in contrast to condensation with aminoguanidine which is independent of pH. A possible explanation for this difference is presented. Chemical and spectral evidence is presented to support the structural assignments for the products.THE thiosemicarbazones and amidinohydrazones of certain ketones and aldehydes have significant antimalarial activity.1$2 Here we describe the syntheses of such compounds from substituted 1,2-and lJ4-naphthoquinones, a study which supplements similar work on the parent and naphthoq~inones.~a*bRecently the reaction of 2-hydroxy-lJ4-naphthoquinone (I) with carboxylic acid hydrazides in 80% aqueous acetic acid was reported to give 2-acylhydrazino-l,4naphthoquinones ; in contrast, reaction in weakly alkaline solution gave 2-hydroxy-lJ4-naphthoquinone 1-acylhydra~ones.~, 5The formation of the conjugate base (Ib) from (I) in alkaline solution, it was proposed, accounted for this behaviour. In a similar way, the quinone (I) reacted 0 0 with thiosemicarbazide in aqueous acetic acid to give 2-thiosemicarbazido-1,4-naphthoquinone (11) and in aqueous sodium hydroxide to give 2-hydroxy-lY4-napthoquinone thiosemicarbazone (IIIa) . In contrast to these reactions, we found that the reaction of the quinone (I) with aminoguanidine carbonate in aqueous ammonium hydroxide or in aqueous trifluoroacetic acid gave 2-hydroxy-l,4-naphthoquinone l-amidinohydrazone (IIIb). Apparently the conjugation form (Ib) exists, even in the trifluoroacetic acid solution of aminoguanidine carbonate, to an extent large enough to effect exclusive condensation a t the l-position. These results indicate that the rate of reaction of aminoguanidine with (Ib) is faster than with (I).4-Thiosemicarbazido-1,2-naphthoquinone '(IVa) and

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