Regioselective Asao-Yamamoto benzannulations of diaryl acetylenes.

Asao-Yamamoto benzannulations transform diarylalkynes into 2,3-diarylnaphthalenes, and regioselective variants of this reaction are of interest for synthesizing substituted polycyclic aromatic systems. It is shown that regioselective cycloadditions occur when one alkyne carbon preferentially stabilizes developing positive charge. Simple calculations of the relative energies of carbocations localized at each alkyne carbon of a substrate predict the regioselectivity, which is not eroded by bulky substituents, including 2,6-disubstituted aryl groups.