Photochromic systems are of special interest in the development of functional materials . Prediction and rational design of new photochromic motifs that can be reversibly switched from one state into another by light has proven challenging. Attempting the backreaction of 18 to 15, we found that the photochemical [1,11] sigmatropic rearrangement is reversible upon irradiation with a 455 nm LED light source. This renders homoannulene ester 15 a structurally novel photochemical switch . The photochromic system can be classified as a p-type photoswitch (backreaction photochemically activated).