in hexane; chloroform under argon, to complex mixt. of hexane and CHCl3 was added and stirred, CF3COOH was syringed in, mixt. was stirred for a few more min; mixt. was filtered, solid was recrystd. from petroleum ether/CH2Cl2, filtrate was distilled in vac., resulting solid was recrystd. from hexane;