Transition-Metal-Free Synthesis of a Known Intermediate in the Formal Synthesis of (-)-Steganacin

The formal synthesis of the two enantiomers of a natural, axially chiral biaryl, steganacin, is reported. The previously developed atropo-diastereoselective coupling of an aryne and an aryllithium ("aryne coupling") allows for this synthesis. In each step, the axial configuration of the biaryl could be maintained. The key intermediate, identified previously, was accessed without using transition metals, which demonstrates the potential of the aryne coupling reaction as a complementary or alternative to transition-metal-catalyzed coupling reactions.