The first attempt was performed by the reaction of cyanuric chloride
1with methyl 4-aminobenzoate 2 in the presence of Na2CO3and methanol
as a solvent (Scheme 2). The reaction was kept at 0 °C for 1 h and
then the temperature was increased gradually to room temperature
and kept for 3–4 h at the same temperature; finally the reaction mixture
was heated at 70–80 °C for 12 h. The progress of the reaction was
followed by TLC (ethyl acetate–hexane; 1:2). After completion of the reaction
the solvent was removed and the product 3 was purified by crystallization
from dichloromethane–hexane (1:2).