Diastereoselective and Synergistic Gold‐Catalyzed Bispropargylation of Xanthones and Thioxanthones: An Access to Xanthene Derivatives

Abstract

A gold‐catalyzed bispropargylation of xanthone derivatives is described. The use of propargylsilanes permits to achieve a deoxygenative bispropargylation through a double catalytic addition of the corresponding allenylgold intermediate to the synergistically activated carbonyl moiety. This methodology works in a diastereoselective manner either with xanthone or thioxanthone derivatives. Monopropargylated xanthydrol silyl ethers were isolated as reaction intermediates and these species could be transformed into symmetrical and non‐symmetrical bispropargylated xanthenes. The formation of non‐symmetrical bispropargylated xanthenes could also be achieved through an one‐pot procedure. Finally, other interesting structures, such as propargylxanthylidenes, propargylxanthenes and bispropargylated xanthenes replacing the silicon moiety, were accessible following different one‐pot synthetic methodologies. In addition, bispropargylated xanthenes could perform a carbonylative [2+2+1] formal cycloaddition.