1-Aminoisoindole as a useful π-system elongation unit

Nitration of 4,7-ethanoisoindoles gave 1-nitro derivatives in moderate yields. Reduction of a nitro to amino group was successfully performed by sodium hydrosulfite in the case of ethyl 3-nitro-4,7-ethanoisoindole-1-carboxylate. The amino derivative was converted to benzylidenaminoisoindoles based on the retro Diels–Alder reaction. Their UV–vis spectra showed strong absorptions at 500–700 nm.