We then explored a PEnT reaction with a substrate of higher ET, the sigmatropic shift of (S)verbenone (ET = 3.0 eV) to chrysanthenone (Table ). This rearrangement has been used in the synthesis of the natural product xishacorene B where verbenone was directly irradiated in the first step with UV light (λexc = 365 nm) yielding 67% chrysanthenone. Schmid et al.