Iron-Mediated Heteroannulation Route to Isochromenones

Significance

The synthesis of a series of 4-H/Se/Te/S-isochromenones via an iron-mediated cyclization of 2-alkynylaryl esters under aerial conditions is reported. The presence of diorganoyl chalcogenides gives rise to 4-substituted isochromen-ones, whereas its absence leads to 4-unsubstituted isochromenones. Solvents other than di­chloromethane lead to lower conversions as did other iron salts. The yields range from moderate to very good, although in some cases the yield was low due to instability of products. The substrate scope was quite well studied, and the method seems to be quite robust, despite the fact that no experiment was repeated in higher than 0.25 mmol scale. Some experiments towards the elucidation of the mechanism were conducted.