Notes: Photochemical Isomerization of trans-Benzalacetone

Influence of the Double‐Bond Geometry of the Michael Acceptor on Copper‐Catalyzed Asymmetric Conjugate Addition

“…The non‐commercially available substrates were prepared according to reported procedures. ( Z )‐1 6 and ( Z )‐2 7 were isolated as the pure ( Z ) compounds by flash chromatography after photoisomerization of the ( E ) substrates using a mercury‐vapour lamp (Scheme ).…”

“…( 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.…”

Photochemical Alkene Isomerization for the Synthesis of Polysubstituted Furans and Pyrroles under Neutral Conditions

“…Building on the seminal report of House, Alexakis and Gilmour independently demonstrated the photochemically enabled isomerization reaction of α–β unsaturated carbonyls from their more stable E geometry to the Z isomer in synthetically useful yields (Scheme , middle) . Alexakis and co‐workers accessed a photostationary equilibrium between E and Z enone isomers through direct excitation of the alkene with a mercury lamp, from which the Z isomer was isolated in 42 % yield.…”