Reaction of pyrroles with naphthoquinones. Synthesis of new pyrrolylnaphthoquinone dyes

The reaction of 1,4‐naphthoquinone (1) with N‐alkylpyrroles (2) gives a mixture of 2‐(pyrrol‐2‐yl)‐1,4‐naphthoquinones (3) and 2,5‐bis(1,4‐naphthoquinon‐2‐yl)pyrroles (4). The yields and the ratios of these two products depend greatly on the experimental conditions. The reaction has been extended to 5‐hydroxy‐1,4‐naphthoquinone (juglone, 5) and 1,2‐naphthoquinone (6). New pyrrolylnaphthoquinones are obtained.