Thioamides and Selenoamides

Synthesis.—The preparation of thioamides and selenoamides is dominated by standard methods of long standing. Many amides of various types, open-chain 

A new thionation reagent, (EtAlS) , is the first product of the reaction of triethylaluminium with hydrogen sulphide it reacts with various dimethylamides to form the corresponding thioamides.  

Thiocarboxylic acids react with isocyanides to give 7V-thioformyl-iV-acylamides 

The thioacylation of NH groups by dithiocarboxylic esters and their salts, as well as by thionocarboxylic esters, is dealt with in Section 5 of this chapter. Diphenylcyclopropenethione reacts with amines to give the cycloadducts (91), which are rearranged to the thioamides (92) when heated in benzene. Thioamides RNHC(S)CHXY are obtained from compounds with active methylene groups by reaction with A-aryldithiocarbamic acid esters, e.g. MeSC(S)NHPh, thiocarbamoyl chlorides, or C-sulphonylthioformamides, 

Thioacylimines (94) are obtained from a-metallated a-isothiocyanatoalkanoic acid esters (93 R = H or Me) with alkyl halides. They rearrange on heating 

Synthesis.— The majority of the papers dealing with the synthesis of thioamides or their selenium andogues report on the application of standard methods. Thus a variety of open-chain aliphatic - - and aromatic as well as cyclic - amides have been converted into the corresponding thioamides by treatment with phosphorus pentasulphide in boiling polar - or, most commonly, non-polar solvents. The action of 

Skaric, B. Gaspert, and D. Skaric, Croat. Chem. Acta, W3, 45, 495. 

Abdel-Lateef and Z. Eckstein, Bull. Acad, polon. ScL, Sir. Sci. chim., 1971,19,705. 

The thiocarbonyl sulphur atom has been introduced into several cyclic thioamides by the reaction of the appropriate cyclic chloro-imines with nucleophiles such as thiourea and the hydrogen sulphide anion. - Some selenopyrrolones (212) have been prepared from the corresponding 3-formyl-2-chloropyrrole by successive treatment of the latter with potassium hydrogen selenide and secondary amines. A reinvestigation of the 

Koltai, J. Nyitrai, K. Lempert, G. Horwath, A. Kalman, and G. Argay, Tetrahedron, 1973, 

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Comparison of the Barriers to Rotation of Amides, Thioamides, and Selenoamides... 

The interest in studying 1 interaction with thioamides and selenoamides arise from their application in both biological chemistiy and material sciences. Thus ... 

The synthesis of j8-j8 -j8"-triaminotriethylamine chelates of the tervalent lanthanide perchlorates have been reported, and isotropic shifts for the paramagnetic complexes were calculated. Lanthanide shifts in the n.m.r. spectra of thioamides and selenoamides have been studied and compared with those values for related sulphur... 

Abstract This presentation is a brief review on the resnlts of our work on iodine interaction with thioamides, selenoamides and amides. The thioamides, benzothia-zole-2-thione (BZT) (1), 6-n-propyl-2-thiouracil (PTU) (2), 5-chloro-2-mercap-tobenzothiazole (CMBZT) (3), N-methyl-benzothiazole-2-thione (NMBZT) (4), benzimidazole-2-thione (BZIM) (5), thiazolidine-2-thione (TZD) (6), 2-mercapto-pyridine (PYSH) (7), 2-mercapto-nicotinic acid (MNA) (8), 2-mercapto-benzoic acid (MBA) (9) and 2-mercapto-pyrimidine (PMT) (10) react with producing three type of complexes of formulae [(HL)IJ(l2) (HL= thioamide and n= 0, 1), [(HL) [I3 ] and [(HL-L)]+[l3 ]. The interaction of seleno-amides, derived from, 6-n-propyl-2-thiouracil (RSelJ) (R= Me- (11), Et- (12), n-Pr- (13) and i-Pr- (14)) with I, have also been studied and produced the complexes [(RSeU)IJ of spoke structure. These complexes are stable in non-polar solvents, but they decompose in polar solvents, producing dimeric diselenide compounds or undertake deselenation. 

In most cases these C,N2 fragments are prepared by reaction of activated carboxylic acid derivatives (C, fragment), such as dithiocarboxylates 2, thioesters 3. nitriles 5, imidates 6, amidines 7, thioamides 8, selenoamides 9, selenoesters 11, orthocarboxylates 14, with hydrazine (N2 fragment) and are transformed to l,4-dihydro-l,2,4,5-tetrazines 17 without isolation. Therefore, these syntheses are treated as a (2 + 1 +2+1) fragment method. 

Reports regarding selenoamides and selenoureas are less than the corresponding thioamides, thioureas, amides and ureas because of instability of compounds including selenium atom and their difficulty in the preparation. Recently, preparation methods to overcome some difficulties have been developed. Their reactions, preparation, application to heterocycles or biological assay systems have been actively investigated. 

Interaction of Thioamides, Selenoamides and Amides with Di-iodine A Study of the Mechanism of Action of Anti-thyroid Drugs... 

Reactions of alkynyliodonium salts with multidentate nucleophiles can be employed for the synthesis of heterocyclic compounds. Recent examples include preparations of thiazoles, selenazoles, and 2-mercaptothiazoles by the treatment of alkynyliodonium mesylates or tosylates with thioamides, selenoamides, and ammonium dithiocarbamate (Scheme 62) [169-171]. A novel hetero-Claisen rearrangement of tricovalent iodine(III) intermediates was proposed to account for the 2,4-disubstitution pattern of the thiazoles [169]. 

HX. As the acid component HX, water leads to the a-aminocarboxamides (42a),14-27-42-47 48 thiosulfuric acid to the thioamides (42b),37 hydrogen selenide to the selenoamides (42c),37 hydrazoic acid to the tetra-zoles (42d)27 39 44,49-52 and hydroxylamines to the amidines (see also ref. 14) and AZ-hydroxyamidines 43... 

Selenoamides, ureas, and hydrazides 700-600 14.29-16.67 s s C=Se str. strongly coupled as with thioamides... 

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