A novel copper(I) catalyzed tandem cycloaromatization has been shown to convert diynals into polycyclic aromatic benzofluorenones. The mechanism of this reaction is presumed to involve the benzopyrylium cuprate, which then adds across the proximal alkyne in a 5-<i>endo</i> sense. Since products have been observed that include an additional equivalent of water, we have investigated the mechanistic role of water by performing this reaction both with a large stoichiometric excess water, and under strictly anhydrous conditions. We also report our attempts to trap the key fulvene cuprate intermediate. We have also examined the use of different metals to catalyze this tandem cyclization, including silver, gold, palladium, nickel, and iron. Our experimental evidence supports the mechanistic hypothesis above, and DFT computations also reveal reasonable transition states for the key 5-<i>endo</i> cuprate addition.

Tandem cyclizations of diynals catalyzed by copper(I): Cycloaromatizations via 5-endo cuprate additions to proximal alkynes

255th National Meeting (2018)

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