A photochemical reaction of a β,γ-unsaturated ketone to form a saturated α-cyclopropyl ketone. The rearrangement formally amounts to a 1,2-acyl shift and 'bond formation' between the former α and γ carbon atoms.
See also: di-π-methane rearrangement
PAC, 1996, 68, 2223. 'Glossary of terms used in photochemistry (IUPAC Recommendations 1996)' on page 2258 (https://doi.org/10.1351/pac199668122223)