Anionic Annulation of 3-Cyanophthalides with Allene Carboxylates: A Carbon-Conserved Synthesis of Naphtho[ b]furanones.

The reaction of 3-cyanophthalides with allene carboxylates in the presence of BuOLi results in a tandem annulation furnishing naphtho[ b]furanones in good yields with no loss of carbon. The carbon economy is explained by a tandem process, in which the initially expelled cyanide induces the second annulation.

Transpositive Tandem Annulation of Phthalides with Allene Carboxylates: Regioselective Synthesis of Arylnaphthalene Lignans.

Allene carboxylates, scarcely used as Michael acceptors, serve as acceptors in the annulation with phthalides in the presence of LDA and provide a one-pot synthesis of naphtho[c]furanones in very good yields. This tandem annulation is proposed to proceed via transposition of the hydroxy group resulting from the initial annulation.

Regiodefined synthesis of brominated hydroxyanthraquinones related to proisocrinins.

Dibromobenzoisofuranone 12, synthesized in six steps, was regiospecifically annulated with 5-substituted cyclohexenones 13/36 in the presence of LiOt-Bu to give brominated anthraquinones 14/38 in good yields. Darzens condensation of 30 was shown to give chain-elongated anthraquinone 32. Alkaline hydrolysis of 38 furnished 39 representing desulfoproisocrinin F.

Synthesis of Vitamin K and Related Naphthoquinones via Demethoxycarbonylative Annulations and a Retro-Wittig Rearrangement.

Anionic annulations of 3-nucleofugal phthalides with α-alkyl(aryl)acrylates involving a demethoxycarbonylation provide a succinct synthesis of vitamin K and related naphthoquinones. Also reported is a new cascade reaction stemming from a Cope-retro-Wittig rearrangement. This cascade leads to direct formation of 1-hydroxy-4-prenyloxynaphthalene-2-carboxylates from the corresponding α-prenyl acrylate acceptors.