Features of a multicomponent Biginelli reaction involving 3-oxobutanoyl-containing podands, aromatic aldehydes, and 1,2,4-triazol-3-amine

A reaction of 3-oxobutanoyl-containing podands with thiophene-2-carbaldehyde (or benzaldehyde) and 3-amino-1,2,4-triazole gave podands featuring a 4,7-dihydro[1,2,4]triazolo[1,5-а]pyrimidine motif. It was established that the process was accompanied by the formation of [4,3-а]-isomers, which occurred in a slight excess during the synthesis of a podand containing a phenyl group at position 7 and, on the other hand, were observed as the minor products during the synthesis of podands bearing a thiophen-2-yl substituent. Trace amounts of monosubstituted podands were also detected, containing a free hydroxy group along with the triazolodihydropyrimidine pharmacophore.