Deciphering the Novel Photoreactivity of β‐Enaminones

Abstract The mechanism of a newly discovered photochemical reaction of β‐enaminones is examined by femtosecond transient absorption spectroscopy and multistate multiconfigurational quantum chemical calculations. Our study reveals that this photochemical reaction features a previously undocumented excited‐state‐proton‐transfer (ESIPT) process. We show that this process is structurally and dynamically gated, occurring in ultrafast time domain with complex progression of β‐enaminone along three potential energy surfaces featuring two conical intersections and a singlet‐triplet crossing.