Reactions of 3-methoxalyl-, 3-polyfluoroacyl- and 3-aroylchromones with dimethyl 1,3-acetonedicarboxylate and 1,3-diphenylacetone in the presence of DBU proceed at the C-2 atom of the chromone system with pyrone ring-opening and subsequent formal [3 + 3] cyclocondensation to functionalized 2-hydroxybenzophenones, 6H-benzo[c]chromenes and benzo[c]coumarins, depending on the substituent at the 3-position. An NMR study and X-ray crystallographic analysis are reported. The compounds synthesized can be considered as promising scaffolds for the design of the novel UV-A/B and UV-B filters.
Organic & Biomolecular Chemistry
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