B(C6F5)3-catalyzed divergent cyanosilylations of chromones dependent on temperature.

A B(C6F5)3-catalyzed divergent cyanosilylation of chromones has been successfully realized. A variety of 4-oxochromane-2-carbonitriles were furnished as kinetic products in high yields via 1,4-cyanosilylations. An unexpected C-O bond cyanosilylation was achieved when the temperature was raised to 80 °C, affording 4-oxo-4-(2-hydroxylphenyl)but-2-enenitriles as thermodynamic products in 72-94% yields, which was confirmed by DFT results.