Amino adds thioamides

In another attractive approach for synthesizing 3,4,5-trisubstituted 1,2,4-triazoles, the molecules are built up from a-amino adds anchored through their amino function to an activated carbonate resin [94]. These urethane-Hnked a-amino acids are coupled with amines. After conversion to thioamides, the trisub-stituted triazoles are obtained by treatment with hydrazines in the presence of Hg(OAc)2. 

Thiazole a,) -dehydro amino add (447) is prepared by cyclization of the corresponding thioamide with ethyl bromopyruvate (Equation (92)). The reaction occurs through the hydroxythiazoline intermediate which dehydrates in the presence of trifluoroacetic anhydride (TFAA) <92CL1005>. 

The presence of a halogen may indicate a haloid salt of a base, alky-l, alkylcue, or aryl halide, add halide, haloid derivative of an aldehyde or aad. Some substances, like mustard oils, amino- uilphonic atids and thioamides, contain both nitiogen and sulphur. 

Ammonium salts of sulphonic acids 98. Sulphonic adds, sulphonamides 98. Amino-sulphonic acids 100. Sulphates of bases 101. Thioureas and thioamides 101. Sulphonyl halides 102. JV-Halosulphonamides 103. Aldehyde and ketone bisulphite compounds 103. Thiols 103. Thioethers 104. Thio-acids 104. Esters of sulphonic adds lOS. 

VIII. Compounds containing sulphur (with or without nitrogen and/or halogen). Ammonium salts of simple and substituted sulphonic acids. Sulphonic acids and their metallic salts sxdphonamides. Amino-sulphonic acids. Siilphates of bases. Thiourea, substituted thioureas, thioamides. Sulphonyl halides. iV-Halogeno-sulphonamides. Aldehyde and ketone bisulphite compounds. Thiols. Thio-ethers. Thio-adds. Esters of sulphonic adds. 

A four-component domino reaction of isatin 58, phenylhydrazine, 3-aminocrotononitrile 117, and cyclic 3-diketones/amide/thioamide 118 in an aqueous medium in the presence of ( )-camphor-10-sulfonic acid on heating at 100 °C for 2-3 h afforded the spiro-fused 2-oxindoles 119 (Scheme 39) [94]. The reaction was successfully extended to 5-chloro- and 5-nitroisatins. According to the proposed mechanism, an acid-catalyzed reaction of phenylhydrazine with nitrile 117 affords the 5-amino-3-methyl-l-phenyl pyrazole 111 that adds to the carbonyl carbon of isatin giving rise to an intermediate product 120. The acid-catalyzed reaction of this intermediate (that has been isolated) with carbonyl compounds 118 affords another intermediate compound 121, which eventually furnishes the final products 119 by cyclodehydration forming tetrahydropyridine ring followed by subsequent dehydration (Scheme 40). 

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