di-π-methane rearrangement

Photochemical reaction of a molecular entity comprising two π-systems, separated by a saturated carbon atom (a 1,4-diene or an allyl-substituted aromatic analogue), to form an ene- (or aryl-) substituted cyclopropane.
Note:
The rearrangement formally amounts to a 1,2 shift of one ene group (in the diene) or the aryl group (in the allyl-aromatic analogue) and 'bond formation' between the lateral carbons of the non-migrating moiety.
D01745
See also: aza-di-π-methane rearrangement, di-π-silane rearrangement, oxa-di-π-methane rearrangement
Source:
PAC, 2007, 79, 293 (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 325