Regioselective syntheses, structural characterization, and electron ionization mass spectrometric behavior of regioisomeric 2,3‐disubstituted 2‐imino‐1,3‐thiazolidin‐4‐ones

Abstract

The regioselective syntheses of 3-alkyl(aryl)-2-(anthracen-9'-ylimino)-1,3-thiazolidin-4-ones (2) and 2-alkyl(aryl)imino-3-(anthracen-9'-yl)-1,3-thiazolidin-4-ones (3) from N-(anthracen-9-yl)-N'-alkyl(aryl)thioureas were accomplished effectively using methyl bromoacetate and bromoacetyl bromide, respectively. Detailed structural characteristics were confirmed mainly by NMR techniques. The mass spectrometric behavior of the resulting sets of compounds of known structures was shown to be characteristic for each set. Some interesting fragmentation pathways involving the transfer and rearrangements of various moieties were also revealed, as well as regioisomerization for particular substituent-specific fragmentations.

Tautomerism, regioisomerism, and cyclization reactions of acridinyl thiosemicarbazides

“…In this work, as part of an examination of thiosemicarbazides containing the acridine moiety (an extension of our long-standing studies with acridine-[8, 10 15] and anthracene-substituted [16,17] thioureas for the purposes of obtaining new and novel type structures concomitant with potential biological applications), we focused on acridines substituted at the urea-type nitrogen atom {Acr NH C(=S) NR NH 2 , prepared from acridin-9-yl isothiocyanate and methyl/phenylhydrazine}. In the following article [6], thiosemicarbazides with acridine on the carbazide side {Acr NH NH C(=S) NH R, prepared from acridin-9-ylhydrazine and isothiocyanates} were examined.…”

Regiospecific synthesis, structure and electron ionization mass spectra of 1,3‐thiazolidin‐4‐ones containing the acridine skeleton

“…In accord with mechanism for reactions of anthracene analogues of 5a-i with bromoacetyl reagents thoroughly discussed in our previous papers [18,19] it was presumed that the reaction of the thioureas 5a-i with methyl bromoacetate was initiated by an attack of sulfur on the α-carbon atom of the ester to afford slowly the alkylation products 6a-i, (Scheme 2) which cyclized in the presence of triethylamine to pure regioisomers 8c-i. However, isothiourea 6a bearing bulky tert-butyl substituent gave rise to a spiro derivative 7a only and isopropyl isothiourea hydrobromide 6b gave in the same conditions a mixture of both spiro and condensation derivatives 7b and 8b, respectively.…”

“…This way, a clear confirmation of the structure of 9 by 13 C NMR that sensitively reflects the sulfur atom directly bound to methylene carbon was impossible; however, proton chemical shifts of 9a-i in the region 4.53-4.73 ppm satisfactorily corresponded to those of a CH 2 group directly bound to a bromine atom (an additive increment of a bromine is +1.97 ppm; that of a sulfur +1.23 ppm). Anthracenyl analogues of 9a-i decomposed during crystallization in methanol back to the starting anthracenyl thioureas [18,19] and no product possessing an S-CH 2 -COOCH 3 moiety that should be formed in hot methanol from an intermediate having an S-CH 2 -CO-Br grouping was found. These facts support S-acylation as a primary step in the reaction of 5a-i with bromoacetyl bromide.…”

“…In recent papers we were trying to synthesize both regioisomers of 2-imino-1,3-thiazolidin-4-ones, using 3-(anthracen-9-yl)-1-alkylthioureas 1 as starting compounds [18,19]. The reaction between 1 and methyl bromoacetate yielded mainly 2-(anthracen-9'-yl)imino-3-alkyl-1,3-thiazolidin-4-ones 2 together with some of the regioisomeric 3-(anthracen-9'-yl)-2-alkylimino-1,3-thiazolidin-4-ones 3 (Scheme 1).…”

Structural revision of products resulting from the reaction of methylhydrazine with acridin-9-yl isothiocyanate due to unexpected acridinyl migration and further reactions

“…Following the collection of crystals from DMF, repeated partial re-solvation of the material using methanol (maintained in an electric field) afforded a final crop of monoclinic crystals belonging to the P2 1 /c space group. Molecular formula, C 17 …”