Synthesis,DFT study and the Eschenmoser sulfide contraction of 1,2,3,4-tetrahydropyrimidine derivatives

5-substituebenzoyl-4-aryl-6-substituephenyl-1,2,3,4-tetrahydro-2-(thioxo,oxo and imino) pyrimidines (4a-d) were synthesized via multicomponent cyclocondensation reaction. 7-benzoyl-8-phenyl-6-(4-carboxyphenyl)-2,3-dihydropyrimido[2,1-b][1,3]thiazin-4(6h)-one (5),6-benzoyl-2-methyl-7-phenyl-5-(4-carboxyphenyl)-3-oxo-2,3-dihydro-5h-thiazolo[3,2-a] pyrimidine (6) and 6-benzoyl-7-phenyl-5-(4-carboxyphenyl)-3-oxo-2,3-dihydro-5h-thiazolo[3,2-a] pyrimidine (7) were synthesized via reactions of starting compound 4e [1] and appropriate reagent compounds. when 4e was treated with α-bromoester in 1,4-dioxane (1/10 ml) it was resulted like the eschenmoser sulfide contraction and compounds 8 was obtained. this method generally requires tertiary phosphine but instead of it we used pyridine as a catalyst. in addition,all synthesized pyrimidine derivatives have been optimized geometrically with dft in gaussian at the b3lyp/6-31g(d,p) level in order to obtain information about the 3d geometries and electronic structures. (chemical equation presented). © 2017,chemical society of pakistan. all rights reserved.