Regiospesific Synthesis of Polysubstituted Phenols via the Palladium-Catalyzed Enyne-Diyne [4 + 2] Cross-Benzannulation Pathway

An efficient method for the synthesis of polysubstituted phenols via the consecutive palladium-catalyzed enyne-diyne [4 + 2] cross-benzannulation reaction and subsequent deprotection step was developed. In all cases, the reactions proceeded in a regiospecific manner affording the corresponding polysubstituted phenols in good overall yields. It was shown that a more useful one-pot methodology could be applied to the synthesis of polysubstituted phenols 4a-e. The synthetically useful p-methoxyphenylacetylene 13 and its monosilylated derivative 12 were smoothly prepared via exhaustive or partial desilylation of bis-silylated aromatic adduct 8c, respectively.