Photochemical access to flavone- and aurone-fused estrone derivatives.

The fusion of privileged heterocyclic scaffolds with biologically relevant structures represents a powerful strategy for developing novel hybrid molecules with enhanced properties. In this work, we report the preparation of flavone- and aurone-fused estrone derivatives via a sequential photo-Fries rearrangement and intramolecular annulation approach. The photo-Fries reaction of estrone 3-phenylpropiolate ester efficiently afforded ortho-hydroxyaryl phenylethynyl ketones, which were further cyclized under basic conditions. The selective formation of flavone (6-endo-dig) or aurone (5-exo-dig) derivatives could be tuned by varying the base strength and solvent conditions. Moreover, the aurone-fused estrone compounds exhibited visible-light-responsive photoisomerization, opening new possibilities for their application as photoswitchable steroidal systems. This photochemical strategy offers a versatile and efficient method to access functionalized steroidal derivatives with potential in chemical biology and material sciences.