Synthesis of 9H-pyrimido[4,5-b]indole derivatives

Abstract

The Vilsmeier reaction of 2-benzyloxycarbonylamidoindole (I) afforded 2-benzyloxycarbonylamido-3-formylindole (II) and N-(3-formyl-2-indolyl)-N', N'-dimethylformamidine (III). Various kinds of 3 acylindole derivatives were synthesized by the same reaction. Reaction of II with benzylamine easily effected condensation-cyclization to produce 3-benzyl-2-oxo-2, 3-dihydro-9H-pyrimido [4, 5-b] indole (VIIa). In order to further extend this reaction, reaction of various 3-acylindole derivatives with various primary amines was carried out and 9H-pyrimido [4, 5-b] indole derivatives listed in Tables I and II were synthesized. Benzylation of VIIa gives two kinds of crystals and it was established that these correspond to 3, 9-dibenzyl-(XL) and 1, 3-dibenzyl-pyrimido [4, 5-b] indole derivatives (XLI) from their elemental analytical values, infrared and nuclear magnetic resonance spectra, and their synthesis by a different route.