Table 1.

Reaction optimization in the isomerization of fumarate scaffold E ‐1.^[a]

Entry	Catalyst	E T [kJ mol−1]	λ [nm]	E:Z
1	benzophenone	289	365	79:21
2	anthracene	178	365	99:1
3	lumichrome	220	402	99:1
4	benzil	227	450	99:1
5	thioxanthone	265	402	1:99
6	–	–	402	99:1
7[b]	thioxanthone	265	402	67:33
8[c]	thioxanthone	265	402	35:65
9[d]	thioxanthone	265	402	3:97

[a] Reactions were performed on a 0.1 mmol scale with 5 mol % of the photocatalyst in dry and degassed acetonitrile (3 mL) and were irradiated for 1 h. The ratio of isomers was determined by ¹H NMR spectroscopy with 1,3,5‐trimethoxybenzene as an internal standard. [b] Irradiated for 1 min. [c] Irradiated for 2 min. [d] Irradiated for 5 min.