Synthesis of substituted 3-amino-4-cyano-1-oxo-1,2,5,10-tetrahydroazepino[3,4-b]indoles

The preparation of 3-amino- and 3-dialkylamino-4-cyanoazepino[3,4-b]indoles bearing substituents on the aromatic nucleus and N-10 is outlined. Starting from suitable substituted ethyl 3-formylindole-2-carboxylates 2, condensation with malononitrile (3) and subsequent sodium borohydride-reduction yielded ethyl 3-(2,2-dicyanoethyl)indole-2-carboxylates 5 and 19, respectively, which were cyclized in boiling alkoxides to 3-alkoxy-4-cyanoazepino[3,4-b] indoles 10,11,20 and 21. This sequence constitutes a novel and flexible route to functional azepino[3,4-b]indoles. The aminolysis of 10,11,20 and 21 with different amines and ammonia yielded the title compounds which were screened for their possible biological activity.