Caesium carbonate promoted regioselective O -functionalization of 4,6-diphenylpyrimidin-2(1 H )-ones under mild conditions and mechanistic insight.

A facile one-step catalyst free methodology has been developed for the regioselective functionalization of 4,6-diphenylpyrimidin-2(1 H )-ones under mild conditions. Selectivity towards the O -regioisomer was achieved by using Cs 2 CO 3 in DMF without use of any coupling reagents. A total of 14 regioselective O -alkylated 4,6-diphenylpyrimidines were synthesized in 81-91% yield. In the DFT studies it was observed that the transition state for the formation of the O -regioisomer is more favourable with Cs 2 CO 3 as compared to K 2 CO 3 . Furthermore, this methodology was extended to increase the O / N ratio for the alkylation of 2-phenylquinazolin-4(3 H )-one derivatives.