Sonogashira coupling of 5-iodouracil (2) and trimethylsilylacetylene gave 5- (trimethylsilylethynyl) uracil (3), which was deprotected to give 5-ethynyluracil (4). Copper (I)- catalyzed cyclization of 4 gave furo [2, 3-d] pyrimidin-2 (3 H)-one (5). Tosylation of 2 and 4 gave the 1-(p-toluenesulfonyl) derivatives 6 and 7, respectively. The tosylated compound 6 and trimethylsilylacetylene did not undergo Sonogashira coupling, and copper (I)- ...