The synthesis and structural functionalization of 6-substituted 2,3-dihydroimidazo[2,1-b] [1,3]thiazol-5-ones

Aim. To extend the synthetic limits of the reaction of the electrophilic intramolecular cyclization (EIC) on the examples of 5,5-disubstituted and 5-yliden substituted 3-allyl-2-thiohydantoins and the directed structural modification of 2-halogenomethyl-2,3-dihydroimidazo[2,1-b][1,3]thiazole-5-ones obtained. Results and discussion. It has been found that the cyclization of 5,5-disubstituted and 5-yliden substituted 3-allyl-2-thiohydantoins under the effect of polyphosphoric acid (PPA), bromine and iodine is an effective method for the synthesis of new 2,3-dihydroimidazo[2,1-b][1,3]thiazole-5-ones. The reaction of the nucleophilic substitution of their 2-halogenomethyl representatives was used to obtain a number of sulfur-containing derivatives and azides. The latter were tested in the reaction of [3+2]-cycloaddition with N-phenylmaleinimide and propargyl alcohol. Experimental part. A series of 2-substituted 2,3-dihydroimidazo[2,1-b][1,3]thiazole-5-ones was synthesized by the reaction of 5,5-disubstituted and 5-yliden substituted 3-allyl-2-thiohydantoins with PPA and halogens with the yields of 66-96 %. A directed modification of the halogenomethyl group of imidazotiazolones produced a series of sulfur-containing derivatives and azides with the yields of 63-93 %. The azides synthesized were used in the [3+2]-cycloaddition reaction with N-phenylmaleinimide and propargyl alcohol leading to 1,2,3-triazoloderivatives with the yields of 51-85 %; their structure was confirmed by the complex spectral analysis. Conclusions. A convenient method for the synthesis of 2-halogenomethyl-substituted imidazo[2,1-b][1,3] thiazoles, which are effective reagents for the directed structural modification by sulfur- and nitrogen-containing functional groups, has been developed.