Copper-mediated synthesis of coumestans via C(sp2)-H functionalization: Protective group free route to coumestrol and 4′-O-methylcoumestrol

A simple and efficient two step synthesis of coumestans is described. The key reaction in the synthesis is the use of easily available Cu(OAc)2 for CH functionalization of 3-(2-hydroxyphenyl)coumarin to give coumestan ring system via formal oxidative cyclization. This approach provided a short protective group free route to naturally occurring coumestrol and 4′-O-methylcoumestrol.

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