Substituted 3-E-Styryl-2H-chromenes and 3-E-Styryl-2H-thiochromenes: Synthesis, Photophysical Studies, Anticancer Activity, and Exploration to Tricyclic Benzopyran Skeleton

A series of densely substituted 2H-chromenes and 2H-thiochromenes were synthesized in good yield through cyanuric chloride-dimethylformamide mediated cleavage of different spiro-4-hydroxychroman-3,1′-cyclopropanes and similar thiochroman analogues. This protocol involves operationally very simple, facile and cost-effective reactions using easily accessible reagents under mild reaction condition with tolerance of a variety of sensitive moieties. Results of steady state and time-resolved absorption and emission spectroscopy highlighted the potential of these compounds as fluorescence probes and designated the suitability for subcellular bioimaging. The prepared 2H-chromenes demonstrated profound cytotoxic activity against MCF-7 cell line. DFT calculations were done on a representative compound where the results indicated promising reactivity of the title compounds as electron-donating dienes. As a continuation, some of these compounds underwent [4 + 2] Diels–Alder cycloaddition with electron-deficient dieno...