Aromatic aldehydes, with aminothiazoles

Antischistosomal activity, of 5-nitro-2-aminothiazoles, 72 Antispasmodic activity, 150, 439 Antitrichomonal activity, 138 of 5-nitro-2-aminothiazoles, 72 Antitubercular activity, 139, 140,441,442 Antitumor activity, 149, 152 Antitussive, 144, 148 Antiulcer properties, 148 Antiviral, 138, 139, 140, 144,438 Appetite depressant, 147 Aprotic solvent, see Solvent effect Aromatic aldehydes, with aminothiazoles, 40... 

Another example of imidazo[2,l-b][l,3]thiazole formation was reported by Adib et al. in their publication concerning eco-friendly catalyst-free MCR in the water [133]. Reaction of cyclohexyl isocyanide with diverse aromatic aldehydes and 2-aminothiazoles in water at 70°C allowed the isolation of heterocycles 96 in good-to-excellent yields (Scheme 43). According to the spectral data, compotmds 96 were determined as single products of the MCR. 

The previously published results [142, 143] devoted to the synthesis of thiazolo [3,2-a]imidazol-2-ones attracted attention of Krasovskii et al. [144] to synthesize corresponding ylidene derivates and to investigate biological activities, promising to be interesting for the medicinal chemistry. By heating 2-aminothiazoles with ethyl bromacetate and a variety of aromatic aldehydes at the appropriate temperature (either 80°C or reflux) in the glacial acetic acid with anhydrous sodium acetate, ylidene derivates of structures 102-104 were isolated (Scheme 48). 

As discussed in Section 3.06.5 aminothiazoles react with alkyl halides to give mainly the product of alkylation at the endocyclic nitrogen when the reaction is conducted in the absence of strong bases with acyl and sulfonyl halides, the exocyclic nitrogen becomes the main nucleophilic site. The reaction of 2-aminothiazoles with heterocyclic or aromatic aldehydes show ample differences depending on the various amine-aldehyde pairs <9lS62i>. In general the azomethine derivatives are obtained by a suitable procedure which has to be followed in each case. The increase of the amine/aldehyde ratio leads to bis-amines as the major products of the reaction. 

For instance, the treatment of 2-aminothiazole or 2-amino-1,3,4-thiadiazole with a equimolar amounts of appropriate (hetero)aromatic or aliphatic aldehydes in the presence of an excess of mercaptoacetic acid under refluxing in anhydrous benzene gave diverse 2-substituted 3-(2-thiazolyl)- and 3-[2-( 1,3,4-thiadiazolyl)]-4-thiazolidinones 115a or 115b, respectively (Scheme 54). 

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