Synthesis of Novel Indeno[1,2-c]isoquinoline Derivatives

Indeno[1,2-c]isochromene was prepared using the readily obtainable starting materials via the condensation of dimethyl homophthalate with 3,4-dimethoxybenzaldehyde in the presence of sodium methoxide in absolute methanol followed by saponification and cyclization with concentrated sulfuric acid at 0°C. The proclivity of cyclized product for undergoing nucleophilic addition has been tested by reaction with nitrogen nucleophiles. Structural assignments are based on spectroscopic data (infrared, 1H NMR, 13C NMR, and mass spectra) and confirmed by the single-crystal x-ray molecular structure (2 and 3).