di-π-methane rearrangement

@P04585@ of a @M03986@ 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.
See also:
aza-di-π-methane rearrangement
di-π-silane rearrangement
oxa-di-π-methane rearrangement
The @R05194@ 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 @M03968@.
PAC, 2007, 79, 293. (Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)) on page 325 [Terms] [Paper]