Synthesis of 4-Substituted C–N Axially Chiral 2-(Trifluoromethyl)-2 H -chromene Indole Derivatives via Central-to-Axial Chirality Conversion

A series of 2H-chromene indole derivatives containing 4-position substituted C-N axially chiral indole and 2-position central chiral trifluoromethyl were synthesized through a Pd-catalyzed asymmetric condensation reaction combined with the strategy of converting central chirality to axial chirality via double-bond isomerization. This method is simple to operate, with a yield of up to 89% and an enantioselectivity of up to 97% enantiomeric excess (ee).