“…( Z )‐4‐Phenylbut‐3‐en‐2‐one [( Z )‐2]: 7 A solution of ( E )‐4‐phenylbut‐3‐en‐2‐one ( E )‐ 2 (10.34 g, 70.73 mmol) in diethyl ether (125 mL) was irradiated with a mercury‐vapour arc lamp (254 nm) for 20 h. The solvent was removed in vacuo, and the crude mixture was purified by flash chromatography (pentane/Et 2 O, 4:1) to afford the desired product in 41 % yield [97 % of the ( Z ) isomer] as a yellow oil. 1 H NMR (300 MHz, CDCl 3 ): δ = 7.46–7.29 (m, 5 H, Ar), 6.85 (d, 1 J H,H = 12.6 Hz, 1 H, CH), 6.14 (d, 1 J H,H = 12.6 Hz, 1 H, CH), 2.11 (s, 3 H, Me) ppm.…”