Ring-Chain Tautomerism of N-Substituted Thiosemicarbazones

Reactions of N-alkylhydrazones of aliphatic ketones

“…Описана також взаємодія гідразонів 97 із ізо-ціанатом калію [59], роданідом калію [60] та сір-ковуглецем [61], яка приводить до азольних спо-лук 98-100 (схема 34).…”

Reaction of 4‐substituted thiosemicarbazides with (2,4,7‐trinitro‐9H‐fluoren‐9‐ylidene)propanedinitrile

“…Chromatographic separ-ation of the residue after concentration gave numerous colored zones, from which products 5a-c and 6a-c could be isolated. In addition, the known compounds 8 [29] and 9,10 [27] were found in small quantities in all cases (Scheme 2). Structural assignments of products 5 and 6 are based on spectral data and on combustion analyses.…”

“…Such ring-chain tautomeric equilibria for aldehyde thiosemicarbazones and their role in mass spectral fragmentation have been discussed before [29][30][31][32][33]. Both 1,2,4-thiazolidine-3-thiones [29,30] (under neutral conditions) and 1,3,4-thiazolidineimines [29,31] (in acidic medium) may exist in equilibrium with the thiosemi- carbazone.…”

“…Both 1,2,4-thiazolidine-3-thiones [29,30] (under neutral conditions) and 1,3,4-thiazolidineimines [29,31] (in acidic medium) may exist in equilibrium with the thiosemi- carbazone. The photochemical cyclization of some aldehyde-semicarbazones to triazolinethiones has also been reported [18], and the differences in the mass spectral fragmentation between thiosemicarbazones and thiosemicarbazones of aldehydes and ketones has been noted early by Djerassi [32] and coworkers who interpreted the fragmentations of thiosemicarbazones to occur from cyclic ions of 1,3,4-thiadiazolium connectivity.…”

Synthesis of novel thiazole and pyrrolothiadiazine derivatives from aldehyde thiosemicarbazones

“…For example, 4substituted 1-phenylacetylthiosemicarbazides undergo cyclization to yield 3-benzyl-2 -1,2,4-triazoline-5-thiones and 2-amino-5-benzyl-1,3,4-thiadiazole, respectively, in the presence of either acid or alkali. The cyclization of suitable open chain organic molecules is a classical and very popular approach to the synthesis of heterocyclic derivatives, owing to both the large variety of heterocycles accessible through this way, and the large variety of conditions under which the reaction can be performed [12][13][14]. Noticeably, when more than one product can be obtained at the same time in a particular reaction, good to excellent selectivities can often be achieved by means of a suitable choice of the cyclizing agent and conditions [15,16].…”