The Characterization and Cycloaddition Reaction of 5,6-Dihydro-1,3-dimethyl-6-methylene-5-[(substituted amino)methylene]-2,4(1<i>H</i>,<i>H</i>)-pyrimidinediones
5,6-Dihydro-1,3-dimethyl-6-methylene-5-[(substituted amino)methylene]-2,4(1H,3H)-pyrimidinedione intermediates (E) were characterized spectroscopically and chemically. The cycloaddition reaction of E with olefinic dienophiles was carried out in highly regio- and stereoselective manners to give quinazoline derivatives.