Visible-light-driven access to Benzo[c]coumarins and a stable cyclohexene-fused intermediate as a robust photocage

Benzo[c]coumarins represent a significant class of pharmacologically active scaffolds. However, their synthesis via visible-light photocatalysis typically relies on pre-functionalized biaryl precursors, leaving atom-economical cascade approaches toward ring-fused architectures relatively unexplored. We herein describe a Ru(II)-catalyzed radical cascade involving homopropargylic alcohol-tethered coumarins and arylsulfonyl hydrazides, where the reaction pathway is divergent based on solvent selection. In MeCN, the sequence affords sulfonyl-functionalized benzo[c]coumarins in yields up to 82%, whereas DMF promotes exclusive formation of a stable, hydroxylated cyclohexene-fused intermediate of IM-2c. Structural characterization via single-crystal XRD analysis and DFT calculations reveals that a polyene-type π∗ character with a LUMO stabilization of 0.417 eV, resulting in a pronounced 65 nm bathochromic shift in IM-2c relative to the benzo[c]coumarin product. Based on this unique electronic profile, IM-2c was modified into a p-methoxybenzoyl ester, which functions as a robust photocage. Irradiation at blue-light triggers rapid photo-elimination (k = 0.1618 s−1, t1/2 ≈ 4.3 s) with an uncaging quantum yield of 0.21, concurrently regenerating the benzo[c]coumarin chromophore. The photolytic process also provides a self-reporting signal through both a hypsochromic shift and a fluorescence-off readout. This integrated strategy streamlines the construction of complex scaffolds and their application in visible-light-triggered cargo release within a unified coumarin-based platform.