Thiazolo 5,4-// pyrimidines, synthesis

Thiazolo[5,4-d]pyrimidine, 2,5,7-trichloro-nucleophilic substitution, 6, 686 Thiazolo[3,2-a]pyrimidine-5,7-diones IR spectra, 6, 672 Thiazolopyrimidines synthesis, 5, 572, 574, 578 Thiazolopyrimidines, amino-purine synthesis from, 5, 591 Thiazolo[3,2-a]pyrimidines synthesis... 

Thiazolo[3,2-a]pyrimidines, synthesis and physiological activity of 89MI10. 

Abdel-Hafez reported the synthesis of fused thiazolo-pyriniidines 104 (Y = NH2, OH) and thiazolo-pyrimidines 105 (R = CN, COOEt) (Scheme 46) by refluxing 103 with active methylene derivatives e.g., diethylmalonate (X = COOEt) or ethyl cyanoacetate (X = CN), or with some aiylidine malonitriles (benzylidinemalononitrile (R = CN and ethylbenzylidinecyano-acetate (R = COOEt)) [71],... 

Among other condensed thiazole ring systems, imidazo[2,l-6]thiazoles (tetramisole is a member of this class), thiazolo-pyrimidines, and thiazolo-pyridines continue to attract the most interest. Attention is concentrated on synthesis and biological activity. Unexpectedly, dihydrothiazolo[3,2-a]pyridinium bromide is readily brominated when the pyridine ring has a 3-nitro-substituent but not when it has a 3-amino-substituent. 

A general scheme, which constructs the thiazolo variety of various bridgehead heterocycles, is basically an extension of HTIB-mediated modification of Hantzsch thiazole synthesis (Scheme 51). Thus, synthesis of 3-substituted-5,6-dihydro-4//-imidazo[2,l-b]thiazoles 202 has been achieved by the treatment of a-tosyloxyacetophenones (generated by the oxidation of 51 with HTIB) with ethylenethiourea [92JCS(P1)707], The method is successfully extended to synthesize 4,5,6,7-tetrahydrothiazolo[3,2-a]pyrimidines 203... 

The one-step synthesis of further tri- and tetracyclic pteridine derivatives from 2-aminopyrazine 153 has also been described <2001JHC1173>. Cyclic analogues of A -[bis(methylthio)methylene]amino reagents such as 2-(methylthio)-2-thiazoline, 5,6-dihydro-2-(methylthio)-4//-l,3-thiazine, 2-(methylthio)-2-imidazoline, 2-(methylthio)-l,4,5,6-tetrahydro-pyrimidine, 2-(methylthio)-2-pyrazine, and 2-chloropyrimidine reacted with aminopyrazine 153 to afford thiazolo/thia-zino[2,3-3]- 159 ( = 1 (53%), n = 2 (42%)), imidazo/pyrimidino[2,l-/ ]- 160 ( = 1 (53%), = 2 (57%)), pyrazino[2,l-/ ]-161 (21%), and pyrimido[2,l-/ ]-pteridine 162 (42%) derivatives, respectively. 

Synthesis of thiazolo[3,2-a]pyrimidines 91MI49. Thiazolo[3,2-a]pyridinium system, synthesis 91KGS1155. 

Fused pyrimidines, formed by a tandem aza-Wittig/electrocycUzation reaction, are used in the synthesis of pyrazolo[3,4-d]pyrimidines, l,2,3-triazolo[4,5-d]pyrimidines and thiazolo[4,5-d]pyrimidine derivatives. ... 

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