Cycloacylation of thioamides and their derivatives by compounds containing an activated multiple bond (review)

Abstract

The cycloacylation reactions of thioamides and their derivatives containing an activated multiple bond are analyzed and summarized.The cycloacylation of thioamides and their derivatives containing an activated multiple bond is an accessible and convenient method for the synthesis of five-and six-membered sulfur-and nitrogen-containing heterocycles -primarily 4H-1,3-thiazin-4-ones [1] and thiazolidin-4-ones [2], and also 2-thioxopiperidines [3], thiopyran-4-ones [4], and pyrimidin-4-ones [5]. Heterocyclic compounds of these types exhibit a wide spectrum of biological activity and have extensive practical applications [1,2,6].This group of reactions is also of interest from the theoretical standpoint since they make it possible to study, analyze, and predict the relationships between the reactivity of substrates containing the ambident NH─C═S group and their structure, reaction conditions, and the nature of substituents at the heteroatoms. Therefore, in spite of the fact that the first papers on this subject were published 50 of more years ago [7,8] synthetic investigations in the field are continuing to this day [9][10][11][12].Nevertheless, no reviews have been published on this subject. It should be mentioned that certain methods for the cycloacylation of thioamides by derivatives of unsaturated carboxylic acids were analyzed in reviews on the synthesis of 1,3-thiazines [1] and thiazolidin-4-ones [2, 13], reactions of N-aminoazolinethiones and N-aminoazinethiones [14], thioamides [15][16][17], and carbon suboxide [18]. However, the information on this subject in these publications has not been coordinated and is not exhaustive.New publications on the cycloacylation of thioamides, in which the range of both reagents and substrates has been extended, have appeared recently. Modern physical methods of establishing the structure of the synthesized products were used, and this made it possible to prove their structure unequivocally.For this reason we attempted to fill the gap and to analyze the information concerning the cycloacylation of acyclic and cyclic thioamides by compounds containing an activated multiple bond. This reviews covers papers not examined in [1,2,[13][14][15][16][17][18] and also papers that have appeared more recently.

Heterocyclization of thioamides containing an active methylene group (review)

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Data from the last six years on the heterocyclization of thioamides containing an active methylene group are analyzed and classified.At the present time there has been a considerable increase in the number of publications on the chemistry of thioamides, and this is explained by the value of the compounds as initial reagents for further transformations and particularly for the synthesis of various sulfur-and nitrogen-containing heterocycles [1][2][3][4][5][6][7][8]. The enormous practical significant of the latter is common knowledge -they have found application as drugs, pesticides, dyes, and preservatives.

Thioamides with an active methylene group are attractive synthesis units for the production of heterocycles.

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“…These polyfunctional compounds can be represented by the formula R 3 -CH 2 CS-NR 1 R 2 (where R 1 , R 2 = H, Alk, Ar; R 3 is an electron-withdrawing group such as CN, AlkCO, ArCO, (AlkO) 2 PO, AlkSO 2 , ArSO 2 , NO 2 ). The presence of another reaction center (the methylene group) makes it possible to use them as N-С-С and S-C-C components for various condensations [1][2][3][4][5][6][7][8]. A special feature of such substrates is the ability to react both with dinucleophilic and with dielectrophilic and dipolar reagents.…”

“…Such characteristics of thioamides with an active methylene group substantially increase their synthetic potential and extend the range of accessible heterosystems, while the use of modern physical methods of investigation (X-ray crystallographic analysis and 1D and 2D NMR spectroscopy) makes it possible to establish the structure of the obtained compounds unambiguously. The presence of biological activity in the products of these transformations also attracts investigators to this subject [5][6][7][8].The reason for the appearance of this review was the increasing need for generalization and classification of new information on the heterocyclization of such thioamides that had not been included in previous reviews [2][3][4][5] and also to define the trends in the study of these processes. Since one of the most important reports in this field is the review [1] we undertook an analysis of the literature that has appeared in the last six years.…”

“…The reason for the appearance of this review was the increasing need for generalization and classification of new information on the heterocyclization of such thioamides that had not been included in previous reviews [2][3][4][5] and also to define the trends in the study of these processes. Since one of the most important reports in this field is the review [1] we undertook an analysis of the literature that has appeared in the last six years.…”

Two Approaches for the Synthesis of Fused Dihydropyridines via a 1,6-Electrocyclic Reaction: Fluorescent Properties and Prospects for Application

“…We can therefore conclude that the reaction proceeds via the addition/condensation mechanism, which was known previously (Scheme 1, I). 6,29,30 However, the investigated transformation did not stop at the cyclization stage and thiazolidinone 7 formation. As the active 1-aza-1,3,5-hexatriene system was created in intermediate compound 7, the 1,6electrocyclic reaction was initiated, and the pyridine ring fused to a thiazolidinone cycle and afforded the new heterocyclic dihydro-5H-thiazolo[3,2-a]pyridine system.…”