A simple, regioselective and high yielding gold-catalyzed synthesis of benzofulvenes, from progargylsilanes and benzophenones, is described. Initially, the carbonyl compound is synergistically activated by the silyl moiety and, for the cyclization step, the gold catalytic activity is clearly increased by the participation of aluminum trichloride, acting as a cocatalyst. Several mechanistic intermediates, such as enynes and silylbenzofulvenes, have been isolated. Different control experiments have been performed, indicating the participation of [LAu][NTf 2 AlCl 3 ] complex as the true catalyst, and revealing a dramatic enhancement of the gold activity by coordination of the Lewis acid to the gold counterion.
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.
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