Quinoxaline-2,3-dithione

G. Reactions and Tautomerism of Quinoxaline-2-thione and Quinoxaline-2,3-dithione (2-Meecapto- and 2,3-Dimercapto-quinoxaline)... 

Quinoxaline-2,3-dithione (2,3-dimercaptoquinoxaline) (90) forms chelates with several transition elements and is used as a colorimetric agent for the detection and quantitative estimation of nickeT and also for the quantitative estimation of palladium. " Nickel gives a pink coloration with (90) in ammoniacal solution, and palladium an orange-red color in AA-dimethylformamide solution containing a little hydrochloric acid. Spectrophotometric studies of the chelate compounds of (90) with Ni(II), Co(II), and Pd(II) in alkaline solu-... 

Quinoxaline-2,3-dithione, as reported earlier,1 is useful for its coordinating properties with transition metals. The metal complexes of the dithione with Cu, Ni, Zn, Pd, and Pt have been prepared,171 and the spectral properties of the Ni and Pd complexes examined.171,172 UV data indicate that quinoxaline-2,3-dithione (153) is present as such, rather than as 2,3-dimercaptoquinoxaline the highly colored nature of its complexes is attributed to charge transfer.171... 

Quinoxaline-2,3-dithione has been prepared fromquinoxaline-2,3-dione by treatment with phosphorus pentasulfide in pyridine. 

Various 3-substituted aminoquinoxaline-2-thiones have been prepared from quinoxaline-2,3-dithione. For example, treatment of the dithione with methylamine yields 3-methylaminoquinoxaline-2-thione, and the corresponding reaction with hydrazine hydrate yields 3-hydrazino-quinoxaline-2-thione. The latter compound is also obtained by treatment of 2,3-dichloroquinoxaline with thiourea and then with hydrazine hydrate. When 2-chloroquinoxaline 1-oxide is heated with thiourea in methanol at room temperature, an unidentified solid m.p. 184-185° is obtained alkaline hydrolysis of methanol-soluble products gives quinoxaline-2-thione in 41% yield. A method of some general applicability is illustrated by the preparation of the thioxo compound 4 from o-anilinoaniline (3). °... 

Many quinoxaline-2,3-dithiones have been prepared from the corresponding 2,3-dichloroquinoxalines by heating under reflux with excess of aqueous potassium hydrogen sulfide solution. The alkali-soluble product on acidification with acetic acid yields the quinoxaline-2,3-dithione. When 2,3-dichloroquinoxaline is treated with two molecular proportions of thiourea in ethanolic solution, S-2-(3-mercaptoquinoxalinyl)-isothiouronium chloride is formed in almost quantitative yield. This on treatment with boiling aqueous sodium hydroxide solution yields quinoxaline-2,3-dithione (15). Substituted quinoxaline-2,3-dithiones have also been prepared by this method. Quinoxaline-2,3-dithione has also been prepared from quinoxaline-2,3-dione by treatment with phosphorus pentasulfide in pyridine, thus avoiding the necessity of first forming the dichloroquinoxaline from the dione. ... 

The acidic dissociation constants of quinoxaline-2,3-dithione are 6.84 and 9.95. The dithione is readily alkylated in sodium hydroxide solution with either methyl sulfate or ethyl iodide to give 2,3-bis(alkylthio)-... 

Dithiolanes have been prepared by the reaction of quinoxaline-2,3-dithiones with geminal dihalogeno compounds, for example, compound 19 is formed from the reaction of the dithione and methylene di-bromide. ... 

Reaction of quinoxaline-2,3-dithiones with acylating reagents gives exclusively S-acylated products. For example, treatment of quinoxaline-... 

Cyclic derivatives have also been prepared from quinoxaline-2,3-dithiones by reaction with phosgene (COClj), thiophosgene (CSCI2), and thionyl chloride (SOCI2). 2,3-Disubstituted quinoxalines result from the reaction of the dithiones with isocyanates, isothiocyanates, and imidoyl chlorides (e.g., PhCCl=NMe). Derivatives of quinoxaline-2,3-dithiones incorporating arsenic, antimony, and tin have been prepared for example, with BujSnCl the 2,3-disubstituted quinoxaline 22 is obtained, and... 

Many acylated derivatives of quinoxaline-2,3-dithione have insecticidal and fungicidal properties. Quinoxaline-2,3-dithione cyclic trithiocarbo-nate (Eradex) (25) and 6-methylquinoxaline-2,3-dithione cyclic dithiocar-bonate (Morestan) (26) are particularly effective. 2,3-Bis(carbethoxy-thio)quinoxaline is reported to have tuberculostatic action. ... 

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