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.