Gold aryne complexes are inferred as transition states in dual gold-catalyzed cyclizations of cis-enediynes. They are better described as ortho-aurophenyl cations, which react with weak nucleophiles and undergo facile intramolecular insertions into C(sp3)H bonds. Indanes, fused heteroarenes, and phenol derivatives are readily prepared using this method. This chemistry represents a dramatic switch from the initial cyclization of the previously observed 5-endo-dig to the 6-endo-dig path in the bifurcation mechanism. Besides its synthetic utility, this chemistry offers, for the first time, insights on the interaction between cationic gold(I) and arynes. This interaction can be viewed as leading to a gold aryne transition state which results in the formation of two regioisomeric ortho-auroaryl cation intermediates, and can be considered to be the result of a shift of the metal along the highly strained CC triple bond. The more stable of these aryl cation forms reacts regiospecifically with a range of nucleophiles in a manner similar to arynes, though the cation should be more electrophilic. While cycloaddition reactions observed with arynes could not be realized, new reactivities with the polarized forms, such as facile intramolecular insertions into C(sp3)H bonds through mesomeric alpha-carbene gold carbenes are realized.

Gold-catalyzed cyclizations of cis-enediynes: Insights into the nature of gold–aryne interactions

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.