An efficient and inexpensive method for the N-alkylation of pyrimidines using ammonium sulfate coated Hydro-Thermal-Carbone (HTC) (AS@HTC) as reused heterogeneous catalyst was developed. The catalyst was characterized by several analytical techniques such as SEM, XRD, and FTIR. The effect ofvarious parameters was studied including catalyst loading, mole ratio, to achieve excellent selectivity and yields in 80–90%. Significantly, the present protocol offers the use of an inexpensive and environmentally friendly catalyst and simple workup. The simplicity of the procedure, excellent yield of the products, and therecyclability of the catalyst are the main advantages of this method.