Add time:08/22/2019         Source:sciencedirect.com

Annulation of 3-nuclofugal phthalides, also known Hauser annulation is a unique reaction for the synthesis of quinonoids embodying the peri‑oxygenated naphthalenes and their higher homologs. It involves the reaction between a C3-nucleofugal phthalide and an acceptor molecule with polarized multiple bond in the presence of a strong base to furnish a naphthalene-1,4-diol or 1,4-naphthoquinone. Many sensitive functional groups tolerate the reaction conditions. Furthermore, the regiochemical integrity is the most attractive feature of the annulation. The interest in the reaction continues to be unabated. This reaction, discovered out of the necessity to construct anthracyclines like doxorubicin in a regiospecific manner, is now applicable to a wide variety of natural products of potential values. Besides being useful for the synthesis of aromatic polyketides like emodin, tetracenomycin D, hypericin and other polyaromatic phenols, the Hauser annulation is found well-suited for the synthesis of angucyclines, pyranonaphthoquines, enediynes, carbazoles, highly condensed coumarins, arylnaphthalene lignans, trioxacarcins, vitamin K, etc.

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