4- Hydroxy-3-thiosemicarbazides

Sodium hydrogen carbonate (s. a. under NaOH) l-Acyl-4-hydroxy- from 4-hydroxy-3-thiosemicarbazides... 

The successful synthesis of stable 4-hydroxy-3-thiosemicarbazides (90)" has opened the way to novel, substituted, 2-hydroxyamino-l,3,4-thiadiazoles (91), by their conventional condensation with imino-esters" or with acid halides R COCl and subsequent dehydrative cyclization. ... 

On the other hand, refluxing 9 in formic acid for 5 h afforded the N-formyl derivative 11 in high yield. Acetylation of 9 by refluxing in acetic acid, afforded acetic acid N -(2-(7-hydroxy-2-oxo-2H-chromen-4-yl)-acetyl)-hydrazide 12 in good yield. Compound 13 was also obtained by refluxing 9 with 3-(2-bromoacetyl)-4-hydroxy-2H-chromen-2-one in ethanol. Reaction of compound 9 with phenyl isothiocyanate in ethanol at room temperature gave 4-phenyl-1 - (7-hydroxy-2-oxo-2 H-chromen-4-acetyl- )thiosemicarbazide 14. 

The basic amino group of the 1-position in semicarbazide or thiosemi-carbazide may be used to react by a substitution reaction with activated halides [52], ethers [51], hydroxy [53], phenoxy [54], and amino groups [55] to yield substituted 1-semicarbazides or thiosemicarbazides. In addition, the amino group of the 1-position may add to electron-deficient double bonds [56]. Formaldehyde and other aldehydes may add to all the available free NH groups to give methylol, alkylol, or polymeric products under basic conditions [57]. Aldehydes or ketenes usually give semicarbazone derivatives, and these in turn are used analytically to identify the purity or structure of a known aldehyde [3]. 

Various extensions are possible (see CHEC 2.19 for full details). Use of aminoguanidines, semicarbazide and thiosemicarbazide gives respectively the 3-amino-1,2,4-triazine, and the 3-one and 3-thione derivatives. Use of a-keto esters and a-keto cyanides gives 5-ones and 5-amino derivatives, respectively. a-Hydroxy ketones afford dihydro-1,2,4-triazines. Intermediates (479) and (480) can sometimes be isolated. 

Thiosemicarbazid 4-Hydroxy-4-methyl-1 -(5-nitro-2-furoyl)-E16a, 192 (Acylier.)... 

Compounds 40 react with guanidine, urea, thiourea, methylisothiourea, guanylthiourea by Lewis-acid catalysis (00S1738) and with thiosemicarbazide, semicarbazide (99IZV361) in the presence of triethylamine to form the corresponding 5,6-oligomethylenepyrimidines and 3-hydroxy-2(thio)-carbamoyl-3-polyfluor-o a 1 k y 1 - 3.3 a. 4.5.6.7 - h e x a h y d r o - 2 / /- i n d a z o 1 e s 41, respectively (Scheme 38). The structure of 41 (thio) is confirmed by X-ray analysis. 

The reaction of 2-amino-4-methyl-l,l,l-trifluoromethyl-2-butene-4-one with thiosemicarbazide forms 5-hydroxy-5-trifluoromethyl-2-pyrazoline, and with derivatives 3-amine-1,2,4-triazoles forms derivatives triazolo[l,5-a]pyrimidine (02IZV332) (Scheme 75). 

Semicarbazide and its derivatives including thiosemicarbazide react with 2-poly-fluoroacyl-cyclohexanones, giving exclusively hydroxy-pyrazolines (99IZV361) (Scheme 107). The choice between the two isomeric possible forms, F and X, was made based on an X-ray investigation (for the derivative with the -C6F13 substituent). 

A soln. of 5-nitrofuran-2-carboxylic acid chloride in dioxane added dropwise to an ice-cooled suspension of an equimolar amount of 4-hydroxy-4-methyl-3-thio-semicarbazide and NaHCOg in dioxane containing some water with stirring, whidi is continued 3 hrs. at room temp. l-(5-nitro-2-furoyl)-4-hydroxy-4-methyl-3-thiosemicarbazide. Y 82%. F. e. and ring closure of the products s. E. Muller and P. Grobner, M. 106, 27 (1975). 

DFT has been used to calculate kinetic, equilibrium, and spectroscopic parameters for the nucleophilic addition/condensation reaction of vanillin (4-hydroxy-3-methoxy-benzaldehyde) and thiosemicarbazide [H2N-C(=S)-NH-NH2]. ... 

One of the classic methods used in qualitative organic analysis to characterize carbonyl compounds depends on the ready formation of crystalline thiosemicarbazones by the action of a thiosemicarbazide on the carbonyl compounds. Not surprisingly, therefore, several recent papers deal with this particular reaction, reporting on investigations of the reaction as such as well as on new examples of its use in synthesis. Carroll and his coworkers found that the course of the reaction of 2-hydroxy-l,4-naphtho-... 

Aliphatic selone esters RC(Se)OEt react with a stoicheiometric amount (0.5 mol) of hydrazine to give hydrazones RC(OEt)=NN=C(OEt)R, and with semi-carbazides and thiosemicarbazides they give 3-hydroxy- or 3-mercapto-1,2,4-triazoles. ... 

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