[Central depressant drugs. 3. 3-Aromatic-aliphatic-substituted 4-hydroxypyrimido-[1,2-a]benzimidazol-2-ones].

Within the structural class of pyrimidol[1,2-a]benzimidazole-2,4-diones accessible through condensation of 2-amino-benzimidazole (1) with malonates (2) there occur representatives exhibiting centrally dampening properties. In particular, aromatic moieties have now been included into the present investigations. By condensation of 1 with diethyl benzylmalonate (2a), 3-benzyl-4-hydroxypyrimido[1,2-a]benzimidazole-2-one (3a) has been synthesized. In the same manner, 4-hydroxy-3-(2'-phenylethyl)pyrimido-[1,2-a]benzimidazole-2-one (3b) has been prepared from 1 and diethyl (2'-phenylethyl)malonate (2b).