Thiobenzamides, 2- synthesis

Furthermore, eight 3-(thiazol-4-yl)-4-hydroxychromen-2-one derivatives were prepared in good yields in the reaction of 3-(2-bromoacetyl)-4-hydroxychromen-2-one with thioureas, thioacetamide, thiobenzamide and ammonium dithiocarbamate. The obtained coumarin derivatives can be used as potentially bioactive compounds and as precursors in the synthesis of medications. 

Thiazolyl metcaptans, from haloallcylthia-zoles, synthesis of, 341 2-Thiazolylphenacyi-bromide, condensation, with thiobenzamide, 194 Thiazolyl phenylketone, by oxidation, 341 Thiazolylphenylsulfoxides, Hammett s relationships, 572 oxidation of, 570... 

Reaction with amides. Benzamides and thiobenzamides are converted to a,a-disubstituted benzylamines. Tertiary amides form ketones on reaction with RCeCl even when the reagent is present in large excess, therefore Weinreb amides are not necessary for the ketone synthesis. Enaminones are also attacked at the carbonyl group, and in the cases of a -silylated derivatives the reaction products are 3,y-unsaturated ketones. ... 

Sakamoto et al. provided an example of absolute asymmetric synthesis involving hydrogen abstraction by thiocarbonyl sulfur [21]. Achiral A-diphen-ylacetyl-A-isopropylthiobenzamide 26a and A-diphenylacetyl-A-isopropyl(p-chloro)thiobenzamide 26b crystallize in chiral space group P2i2i2i (Scheme 13). Photolysis of the chiral crystals in the solid state gave optically active azetidin-2-ones 27, whereas achiral thioketones 28 were obtained as main products. When 26a was irradiated in the solid state at - 45°C followed by acetylation (at - 78°C), 2-acetylthio-3,3-dimethyl-l-diphenylacetyl-2-phenylaziridine (30a 39% yield, 84% ee), 4-acetylthio-5,5-dimethyl-2-diphenylmetyl-4-phenyloxazoline (31a 10% yield, 50% ee), 3,3-diphenyl-l-isopropyl-4-phenylazetidin-2-ones (29a 16% yield, 20% ee), thioketone (28a 15%) and A-isopropylthiobenzamide (15%)... 

The synthesis of thiazoles 43 adds an element of regioselectivity as the thioamide has soft (S orbital controlled) andhard (N charge controlled) nucleophilic sites anditis essential to differentiate equally clearly between the two electrophilic centres on the carbonyl part of the molecule. We need to know that a thioamide will react with an a-haloketone 48 X = Cl, Br so that the hard nitrogen atom attacks the ketone and the soft sulfur atom attacks the saturated carbon atom. Thus the simple non-steroidal anti-inflammatory drug Fentiazac 50 is made from thiobenzamide 51 and the simple bromoketone 52, made in turn by bromination of the ketoacid. The synthesis is just that.3... 

Stevens et al. have proposed another likely mechanism for the Jacobson synthesis where a single-electron transfer process appears to operate. Here thiobenzamide reacts with the base to generate thiolate ion that undergoes oxidation to form a thiol radical shown below. The thiol radical can attack the unsubstituted ortho position and form a five-membered ring that aromatizes through the elimination of a hydrogen radical and form benzothiazole. Stevens et al. during this study also noted that the availability... 

Mayhoub AS, Kiselev E, Cushman M (2011) An unexpected synthesis of 3,5-diaryl-1,2,4-thiadiazoles from thiobenzamides and methyl bromocyanoacetate. Tetrahedron Lett 52 4941 943... 

Metal Complexes.—In order to determine the effect of the presence of a nitrogen donor on the ortho-metallation of the thiobenzoyl function, Alper and Chan treated NN-dimethylthiobenzamide with di-iron enneacar-bonyl. However, no sulphur-donor ligand ortho-metallated complex was obtained, as happens in the case of thiobenzophenone, but instead the complexes (245) and (246) were formed. - NN-Dimethylthioacetamide similarly yielded the complexes (247) and (248), whereas the unsubstituted thiobenzamide on treatment with di-iron enneacarbonyl gave the complexes (249) and (250). The synthesis and properties of metal complexes of dithio-oxamides, dithiomalonamides, 2-thiocarbamoyl-l,10-phenan-throlines, thiomorpholine-3-thione, and 2,4-dithiouracil have also been described recently. 

Thiobenzamide has been reported to undergo a Mannich-type reaction on simultaneous treatment with aldehydes and arylsulphinic acids, yielding the compounds (267). 2-, 3-, and 4-thiocarbamoylpyridines similarly gave the N-(aminomethyl)thioamides (268) by reaction with a variety of amines in the presence of formaldehyde. A new stereospecific synthesis of 5,6-di-hydro-4H-l,3-thiazines (269) depends on the reaction of thioamides with aldehydes and alkenes it was considered likely that (270) is an intermediate in this reaction. 

Barton, D. H. R. and Samadi, M., The invention of radical reactions. 25. A convenient method for the synthesis of the acyl derivatives of N-hydroxypyridine-2-thione, Tetrahedron, 48, 7083,1992. Garner, R, Anderson, J. T. and Dey, S., S-(l-oxido-2-pytidinyl)-l,l,3,3-tetramethylthiouronium hexafluorophosphate a new reagent for preparing hindered barton esters,/. Org. Chem., 63,5732,1998. Prabhakar, S., Lobo, A. M., and Santos, A., A, Convenient method for the synthesis of N-hydroxy thiobenzamides (C-arylthiohydroxamic acids). Synthesis, 829,1984. 

Oda, K., Tsujita, H., Sakai, M., and Machida, M., Photochemistry of the nitrogen-thiocarbonyl systems. Photoreaction of thiobenzamide with 2-vinylfuran analogs. Facile synthesis of tetracyclic indole system, Heterocydes, 42, 121, 1996. 

---