Synthesis of Hexasubstituted Carbamimidic Acid Anhydrides and of<i>N</i>
<sup>1</sup>,<i>N</i>
<sup>1</sup>,<i>N</i>
<sup>2</sup>-Trisubstituted Formamidines from 1,1,3-Trisubstituted Ureas
1,1,3-Trisubstituted ureas 1 were converted with phosphoryl chloride to hexasubstituted carbamimidic acid anhydrides 2 which were hitherto unknown or difficult to prepare by other methods. The ureas bearing bulky substituents were converted to amidinoyl chlorides 3 which were reduced to the corresponding formamidines 5 with amine-boranes in acid.