In previous work, we were the first to establish the feasibility of a one-step synthesis of the 1,2,3,6-tetrahydroindeno[2,1-c]azonine [1] and 1,2,3,4,7,12-hexahydroazonino[4,5-b]indole heterocyclic systems [2], which had previously been difficult to obtain, in the reaction of quaternary 2,3-dihydro-1H-indeno-[2,1-c]pyridinium or 1,2,3,4-tetrahydro--carbolinium salts with dimethyl acetylenedicarboxylate (2) in the presence of base. Gimranova [3] has also undertaken an attempt to convert a series of N-(ethoxycarbonylmethyl)-1,2,3,4-tetrahydroisoquinolinium halomethylates by an analogous method into 2,3,4,7-tetrahydro-1H-benzo[d]azonines. However, in this case, the expected products could not be isolated or even detected by HPLC/MS. In the present work, we report the cascade synthesis of the first representative of the tetrahydro-1H-benzo[d]azonine system. This system was formed upon the action of 20% aq. NaOH on a mixture of DMADC 2 and quaternary salt 1 containing a N-cyanomethyl group at 20°C over 20 h and isolated by preparative chromatography in 72% yield. The mass and IR spectral data and elemental analysis results confirmed the chemical formula of diester 3.
