Phosphine-Catalyzed (4 + 2) Annulation of Allenoates with Benzofuran-Derived Azadienes and Subsequent Thio-Michael Addition.

A phosphine-catalyzed (4 + 2) annulation of tetrahydrobenzofuranone-derived allenoates and benzofuran-derived azadienes (BDAs) has been achieved to construct the decahydro-2 H -naphtho[1,8-bc]furan derivatives, which were subsequently treated with 4-methylbenzenethiol and trimethylamine to produce thio-Michael addition products in high to excellent yields with good diastereoselectivities.