Two approaches to the synthesis of boron-substituted pyrimidines and borazaroquinazolines (1) have been ex-plored First,(dibutoxybory1) ethene and bromomalononitrile were converted to l, l-dicyano-3-bromo-3-(dibutoxy-bory1) propane (2), which was reduced with triphenyltin hydride to l, l-dicyano-3-(dibutoxyboryl) propane (3), which condensed with thiourea to yield 2-mercapto-4, 6-diamino-5-(2-dihydroxyborylethyl) ...