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Ligand-Controlled Product Selectivity in Gold-Catalyzed Double Cycloisomerization of 1,11-Dien-3,9-Diyne Benzoates

Philip Chan’s group have this week published a paper in Journal of the American Chemical Society describing a synthetic method to prepare tricyclic bridged heptenones and hexenones from gold(I)-catalyzed double cycloisomerization of 1,11-dien-3,9-diyne benzoates. The work found a divergence in product selectivity could be achieved by fine-tuning the steric nature of the ligand of the Au(I) catalyst. In the presence of the catalyst [MeCNAu(JohnPhos)]+SbF6-, a tandem 1,3-acyloxy migration/metallo-Nazarov cyclization/1,6-enyne addition/Cope rearrangement of the substrate selectively occurred to afford the seven-membered ring system. In contrast, with the [MeCNAu(Me4tBuXPhos)]+SbF6- catalyst, the 1,11-dien-3,9-diyne benzoate was observed to undergo a more rapid tandem 1,3-acyloxy migration/metallo-Nazarov cyclization/[4 + 2]-cyclization pathway to give the bridged hexenone.

The full article is available online at http://pubs.acs.org/doi/pdf/10.1021/jacs.5b02377

Wed 20 May 2015, 16:00