Copper-catalyzed oxidative cross-dehydrogenative coupling of 2H-chromenes and terminal alkynes

摘要

An efficient copper-catalyzed cross-dehydrogenative coupling of 2H-chromenes and terminal alkynes mediated by DDQ has been established. Protic additive EtOH proved to be crucial to harmonizing the oxidation with subsequent alkynylation step by retaining the oxidation state of oxocarbenium ion in the form of acetal. The CDC reaction exhibits good substrate scope, with a range of terminal aryl- and alkyl alkynes well tolerated. The copper-catalyzed alkynylation of 2H-chromene acetals with terminal alkynes were also explored.