Thiosemicarbazone and amidinohydrazone derivatives of some 1,4-naphthoquinones

Abstract

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

Studies of the Functionalized α-Hydroxy-p-Quinone Imine Derivatives Stabilized by Intramolecular Hydrogen Bond

“…Interestingly, in the case of aminoderivatives of quinone 1 (a merocyanine on the base of the o-quinone form), deep-blue colored crystals were obtained [17,19]. In general, derivatives containing aroyl hydrazine fragments were expected as a result of such substitution [15,20], and a few tautomeric structures can be supposed for the products [21,22]. For the compounds obtained (3a-g), the structure determination of the quinone/substituent fragments (Scheme 1b) can explain the observed difference in color of crystals 3a-g in comparison to aminosubstituted derivatives of quinone 1a.…”

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

“…Semicarbazides and thiosemicarbazides are substances used to identify aldehydes and ketones, are very versatile in the synthesis of heterocycles, and have several applications in the preparation of important drugs. Nucleophilic nitrogen semicarbazides can easily add to carbon C4 of β-NQSNa ( 18 ) to produce 1,2-naphthoquinones containing these groups [ 87 ]. This is a reaction very similar to adding amines to 18 .…”

New homoleptic imine derivative of lawsone and its metal complexes: Preparation, characterization, in vitro and in silico biological investigation

“…Carroll et al synthesized the imine derivative of lawsone from thiosemicarbazide. 14 Condensation of lawsone and 2(2 0 -aminoethylpyridine) had been reported by Thube et al 15 They have concentrated on the Hatree Fock and the density functional theory (DFT) studies of the Schiff base ligand. Copper chelates of thiosemicarbazone-lawsone Schiff base ligands were prepared by Chikate et al and analysed for EPR and redox studies.…”

“…So far, the imine derivative of lawsone was reported in a few articles. Carroll et al synthesized the imine derivative of lawsone from thiosemicarbazide 14 . Condensation of lawsone and 2(2′‐aminoethylpyridine) had been reported by Thube et al 15 They have concentrated on the Hatree Fock and the density functional theory (DFT) studies of the Schiff base ligand.…”