Thiosemicarbazides semicarbazides

Triazole. RingschluB zu 1.2.4-Triazolderivaten (XLIII) er-folgt, wenn s-Triazin auf Verbindungen vom Typ des Semicarbazids, Thiosemicarbazids und Aminoguanidins einwirkt (24). 

Substituted hydrazine or derivative Reagents Semicarbazide, thiosemicarbazide, or semicarbazone Ref. 

Diacetyl monoxime + semicarbazide, thiosemicarbazide or selenosemicarbazide [Cr(LH)L] [Cr(LH)(H20)3lCl2 (semicarbazone only) 20... 

The reaction of 1,2-dicarbonyl compounds with amidrazones, semicarbazide, thiosemicarbazide and aminoguanidine has also been used for the synthesis of condensed 1,2,4-triazines. Cyclohexane-, cycloheptane- and cyclooctane-1,2-diones (489) with amidrazones (453) afford the cycloalkatriazines (490) (78HC(33)189, p.66l). 

Triphenylgermyl-4-propiono-substituted semicarbazides, thiosemicarbazides PhtGe CHR,CH2CONHCHC(X)NHR" (R = H, Ph R" = Ph, p-tolyl X = O, S) and their heterocyclic derivatives have been found to possess inhibitory effects on gastric carcinoma MGC-803 in vitro137. 

Further nucleophilic reagents used to cleave 2-amino-l,3,4-oxadiazoles include alcoholic potash, primary amines, hydrazine hydrate, phenylhydrazine hydrochloride, acid hydrazides, semicarbazide, thiosemicarbazide, ammonium hydrogen sulfide, and hydrochloric acid. 

The 1,4-dinucleophilic building blocks used most are 1,2-disubstituted ethanes of the type HXCHiCHjYH, semicarbazides, thiosemicarbazides, hydroxamic acid amides, amidrazones, and 1,2-disubstituted aromatic and heteroaromatic compounds. 1,1-Dielectrophilic building blocks preferentially used are perfluorinated carboxylic acids and their derivatives, such as acid halides, anhydrides, imidoesters, nitriles, perfluoroalkyl chlorosul-... 

Cis isomers are preferentially used. Trans isomers are reported to be less reactive or failed to give pyridazines. However, some hydrazones of trans isomers, upon heating in glacial acetic acid, form 14 and the reaction involves slow isomerization as indicated with dibenzoylethylene.332 Here, the cis isomer forms immediately (14, Rj = Rg = H, R = R3 = Ph) in almost quantitative yield at room temperature, whereas the trans isomer upon heating with hydrazine in acetic acid gives the same product in low yield. Instead of hydrazine, semicarbazide, thiosemicarbazide and aminoguanidine have also been used to build up the pyridazine ring. ... 

In addition to amidrazones, the corresponding carbonic acid derivatives semicarbazide, thiosemicarbazide, selenocarbazide, guanidin-2-amine, guanidine-1,2-diamine and 3-methylisothiosemicarbazide can also be reacted with 1,2-dicarbonyl compounds, leading to the nonaromatic 1,2,4-triazin-3(2//)-oncs,451 1,2,4-triazine-3(2/f)-thiones,452 -3(2//)-selenones 5,453 or the aromatic l -triazin-S-amines,112 3-hydrazino-l,2,4-triazines,113 or 3-(methylsulf-anyl)-l,2,4triazines 6.114 The initially formed hydrazones can be isolated in most cases and cyclized in a second step, but isolation is not necessary as direct cyclization is usually achieved without problem. 

The use of /l-alkyl-/l-methoxyvinyltrifluoromethylketones aifords various heterocycles with a CF3 group (95JHC739). Thus, cyclocondensation has been performed with hydroxylamine, semicarbazide, thiosemicarbazide, phenylhydrazine, and urea. 

The reactions of acylcyanides with amidrazones 209, semicarbazides, thiosemicarbazides 218, and aminoguanidines 228 result in the formation of 5-amino-l,2,4-triazines <2004SOS(17)357>, 5-amino-l, 2,4-triazin-3-ones, the corresponding 3-thiones, and 3,5-diamino-l,2,4-triazines <2003TL5657, 2004SOS(17)357> (Scheme 143). 

Compounds 98 are converted relatively easily to five-membered heterocycles. 1,2,4-Triazoles 102 are obtained in high yield by reactions of 98 with hydrazine derivatives (aryl hydrazines, semicarbazide, thiosemicarbazide, benzhy-drazide, and aminoguanidine) (Scheme 7). The corresponding reaction with hydroxylamine hydrochloride affords... 

N-1 benzoxazolyl 3,4-dihydropyrimidinones/thiones 33 have been obtained by reacting carbomethoxy benzoxazole 30 with semicarbazide/ thiosemicarbazide 31 (X = O, S) in refluxing ethanol using a catalytic amount of piperidine to obtain intermediate 2-(2- alkylbenzoxazole-5-car-bonyl)hydrazine carboaxo/thioamide 32 (R = H, Me X = O, S), which upon cyclocondensation with an aromatic aldehyde and p-ketoester in the presence of tiifluoromethane sulfonic acid at room temperature afforded benzoxazolyl 3,4-dihydropyrimidin-2(lH)-ones/thiones 33 (R = H, Me R = Me, CF3), in excellent yield (Scheme 12) (09M16). 

Reactions of Pyrrole-2-carbaldehydes with Hydroxylamine, Semicarbazide, Thiosemicarbazide, and Aminoguanidine... 

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