Synthesis from thioamides

Synthesis from thioamides. Compounds prepared using thioamides include 4-(4-chlorophenyl)-2-[4-(hydroxy or acyl)phenyl] thiazol-5-ylacetic acids,2-(hydroxyphenyl)thiazole-4-carboxylic acids and derivatives, and substituted... 

Synthesis from Thioamides and Related Compounds. Type B, CgHs—N-—C—S.) The action of a large excess of thionyl chloride on substituted thioureas of type (22) (incorporating a jS-hydroxy-group in their Aralkyl group) produces 2-aminobenzothiazole derivatives (23) preferentially, rather than thiazolines (24) or oxazolines. Thionyl chloride, like sulphuryl... 

The Hantzsch thiazole synthesis from thioamides and a-halogeno-ketones has been applied to iVAr-(dimethyl)dithio-oxamide to give 2-(dimethylthio-carbamoyl)thiazoles, but in some cases it took another course. Thus, 1-alkylthiocarbamoyl-l-cyanoacetophenones (91) react with bromo-ketones with elimination of alkylamine, giving 2-methylidene-l,3-oxathioles (92). The thio-anilide of acetoacetic acid reacts with 2-bromo-l-tetralone to give the spiro-... 

Likewise, benzothiazole synthesis from thioamides 9 has been accomplished by a Cu(I)/Pd(11)-mediated ortho-C-H-functionaUzation/intramolecular C-S-bond formation process [365]. 

There is an enormous literature on thiocarbonyl compounds, due in part to the technical and industrial importance of many of them, including thioamides, thioureas, xanthates, dithiocarbamates and so forth. An excellent, and recent, general review is available.107 There are also specialized reviews germane to the present chapter Griffin, Woods, and Klayman2 discussed the use of thioureas in the synthesis of heterocycles the preparation of thiazoles from thioamides is included in a three-part volume on Thiazoles 108 the use of carbon disulfide in the synthesis of trithiones and related heterocycles has been reviewed by Mayer109 and Huisgen110 has reported numerous examples of 1,3-dipolar cycloadditions in which carbon disulfide was used. 

Selected examples of the synthesis of thioamides from nitriles ... 

Preparation of thiazole Hantzsch synthesis can be applied to synthesize the thiazole system from thioamides. The reaction involves initial nucleophilic attack by sulphur followed by a cyclocondensation. 

Isothiazole synthesis Isothiazole can be prepared from thioamide in the following way. 

Crystal-to-Crystal Solid-State Photochemistry Absolute Asymmetric (3-Thiolactam Synthesis from an Achiral a,(3-Unsatur ated Thioamide, J. Am. Chem. Soc. 118, 10664-10665. (b) Sakamoto, M., Takahashi, M., Arai, W., Mino, T., Yamaguchi, K., Watanabe, S., and Fujita, T. (2000) Solid-State Photochemistry Absolute Asymmetric (3-Thiolactam Synthesis from Achiral N,N-Dibenzyl-a,6-unsaturated Thioamides, Tetrahedron, 56, 6795-6804. (c) Hosoya, T., Ohhara, T., Uekusa, H., and Ohashi, Y. (2002) Crystalline-state... 

Hydroxythiazole, from chloroacetaldehyde and ammonium thiocaibamate, 258 4-Hydroxy-2-thiazolecarboxylic acid ethyl ester, self condensation of, 294 synthesis of, from ethylcyanoacetate and ethylthioglycolate, 294 from thioamides and a-haloacids or esters, 294... 

Thioamide synthesis from dithiocarboxylates and amines under basic conditions gives thiols as rather unpleasant parallel products. This problem is avoided by using S-thioacylated thioglycolic acids (17), as... 

Crystalline adducts from thioamides and aromatic acid chlorides ate well known. A very convenient synthesis of diacyl sulfides and thiocarboxylic acids - proceeds via adducts of thio-DMF with acid chlorides. 

Sulfur can be activated by the presence of bases, e.g. amines (R2NH). Such proton-bearing amines cleave the S8 ring and also will react with the thiolation products. This procedure is used in the synthesis of thioamides (9) from the methylarenes (10) (Scheme 5). 

A general synthesis of thioamides from nitriles which utilizes thioacetamide as the source of hydrogen sulfide under acidic conditions is reported by Taylor and Zoltewicz.1 The thioamides are formed in good yield and high purity and the method is equally applicable to aliphatic nitriles and to aromatic nitriles containing either electronreleasing, electron-withdrawing, or potentially reducible substituents. One equivalent of the nitrile is heated on a steam bath for 15-30 min. with 2 eq. of thioacetamide in s s... 

Synthesis of enamino ketones from thioamides or of (3-dicarbonyl derivatives from thioesters. 

Synthesis from o-isoascorbic acid Syntheses of 2 and its antipode 37 from the commercially available D-isoascorbic acid have been reported by conversion to the enantiomerically pure acetonide lactone 29 on a large scale in 75% yield (Scheme 5). Lactone 29 was treated with amino vinylsilane 30 to give the amide 31 in 82% yield, which was used in two different ways. Mitsunobu conditions were not successful to convert 31 to 32. However, the conversion has been achieved in 88% yield by mesylation and then subjection to intramolecular cyclization. Treatment of 32 with Lawesson s reagent afforded the respective thioamide, which was treated with BFj OEtj followed by direct reduction with LiBEtjH to provide the 2-(ethylthio)pyrrolidine 35. Cyclization of 35 afforded the single stereoisomeric tetrahydroindolizine 36. Catalytic hydrogenation of 36 followed by deprotection provided 2-cp/-lentiginosine (2). 

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