NOVELTY - Synthesis of 1,3-diphenyl-(1H,3H)-6-methylpyrimidine-2,4-dione involves carrying out Chapman rearrangement of 2,4-diphenoxy-6-methylpyrimidine at 170 degrees C for 70 minutes.    USE - Synthesis of 1,3-diphenyl-(1H,3H)-6-methylpyrimidine-2,4-dione used as antiviral agent, antineoplastic agent, pesticide, anti-photosynthetic herbicide, and insecticide, and for treating or preventing dyslipidemia, neurological disorders, hematological diseases, cancer, inflammation, respiratory diseases, gastroenterological diseases, diabetic complications, non-alcoholic fatty liver diseases, and leukemia.    ADVANTAGE - The method enables synthesis of 1,3-diphenyl-(1H,3H)-6-methylpyrimidine-2,4-dione with high yield, by simple and environmentally-friendly process.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) synthesis of 1,3-di-(2-naphthyl)-(1H,3H)-6-methylpyrimidine-2,4-dione, which involves carrying out Chapman rearrangement of 2,4-di-(2-naphthoxy)-6-methylpyrimidine at 178 degrees C for 100 minutes;    (2) synthesis of 1,3-di-(2-carbethoxyphenyl)-(1H,3H)-6-methylpyrimidine-2,4-dione, which involves carrying out Chapman rearrangement of 2,4-di-(2-carbethoxyphenoxy)-6-methylpyrimidine at 175 degrees C for 90 minutes;    (3) synthesis of 1,3-di-(4-carbmethoxyphenyl)-(1H,3H)-6-methylpyrimidine-2,4-dione, which involves carrying out Chapman rearrangement of 2,4-di(4-carbmethoxyphenoxy)-6-methylpyrimidine at 185 degrees C for 80 minutes;    (4) synthesis of 1,3-di-(4-carbethoxy-2, 6-dimethoxyphenyl)-(1H,3H)-6-methylpyrimidine-2,4-dione, which involves carrying out Chapman rearrangement of 2,4-di-(4-carbethoxy-2,6-dimethoxyphenoxy)-6-methylpyrimidine at 180 degrees C for 90 minutes;    (5) synthesis of 1,3-di-(2-ethoxyphenyl)-(1H,3H)-6-methylpyrimidine-2,4-dione, which involves carrying out Chapman rearrangement of 2,4-di-(2-ethoxyphenoxy)-6-methylpyrimidine at 160 degrees C for 65 minutes;    (6) synthesis of 1,3-di-(3-ethoxyphenyl)-(1H,3H)-6-methylpyrimidine-2,4-dione, which involves carrying out Chapman rearrangement of 2,4-di-(3-ethoxyphenoxy)-6-methylpyrimidine at 175 degrees C for 85 minutes;    (7) synthesis of 1,3-di-(4-chloro-3,5-dimethylphenyl)-(1H,3H)-6-methylpyrimidine-2,4-dione, which involves carrying out Chapman rearrangement of 2,4-di-(4-chloro-3,5-dimethylphenoxy)-6-methylpyrimidine at 180 degrees C for 80 minutes; and    (8) synthesis of 1,3-di-(4-methylphenyl)-(1H,3H)-6-methylpyrimidine-2,4-dione, which involves carrying out Chapman rearrangement of 2,4-di-(4-methylphenoxy)-6-methylpyrimidine at 175 degrees C for 90 minutes.