For example, when tetrahydrofuran is used as the reaction solvent, the reaction mixture is poured onto a cold saturated aqueous solution of ammonium chloride, followed by separation of the tetrahydrofuran layer; the aqueous layer is ex- 'tracted with a small amount of diethyl ether and combined tetrahydrofuran and ether extracts are dried over a suitable drying agent such as sodium sulfate, follow