1: With lithium hexamethyldisilazane in tetrahydrofuran T=-78°C; 0.75 h; Inert atmosphere; 2: With trifluoromethylsulfonic anhydride in tetrahydrofuran T=-78°C; 1.25 h; Ineret atmosphere; Further stages;

n-butyllithium; boron trifluoride diethyl etherate 1) THF; 2) -20 deg C, 0.5 h; 3) -20 deg C, 1.5 h; Yield given. Multistep reaction;