Enantioselective copper-catalyzed intramolecular phenolic O-H bond insertion: synthesis of chiral 2-carboxy dihydrobenzofurans, dihydrobenzopyrans, and tetrahydrobenzooxepines.

Efficient: A copper-catalyzed enantioselective intramolecular insertion of carbenoids into phenolic O-H bonds has been developed. This method can be used for the synthesis of the title compounds in high yields and excellent enantioselectivities under mild and neutral conditions. NaBAr(F)=sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate.