Syntheses of 12H-benzo[a]xanthen-12-ones and benzo[a]acridin-12(7H)-ones through Au(I)-catalyzed Michael addition/6-endo-trig cyclization/aromatization cascade annulation

A multifaceted gold(I)-catalyzed aromaticity-driven double 6-endo cascade cyclization strategy to synthesize both 12H-benzo[a] xanthen-12-ones and benzo[a] acridin-12(7H)-ones, whose core motifs xanthone and acridone both exist as important scaffolds in an immense number of bioactive compounds, was developed. The scopes of this strategy were examined by using a batch of synthetic 1,3-diphenylprop- 2-yn-1-one substrates. To probe the mechanism of this cyclization a control experiment for synthesizing intermediates was performed. Thus, a putative mechanism was determined according to this experiment and previous studies.