Conjugated diene complexes electrocyclic ring closure

Photochemical electrocyclic ring-closure in a 4-electron system works well for many acvclic dienes (2.17) and related cvclic systems (2.18). The situation with conjugated trienes is more complex, and they can act as 6-e ectron systems (2.19) leading to cyclohexal, J-dienes, or as 4-electron systems (2.20) giving cyclobutenes. In addition they can undergo other photochemical reactions such as geometrical isomerization about the central double bond (which must be cis if a 6-electron electrocyclic nng-closure is to take place). [Pg.120]

See also in sourсe #XX -- [ Pg.198 , Pg.210 , Pg.212 , Pg.213 , Pg.214 , Pg.215 , Pg.216 , Pg.217 , Pg.218 , Pg.219 , Pg.220 , Pg.221 , Pg.222 , Pg.223 ]

See also in sourсe #XX -- [ Pg.198 , Pg.210 , Pg.212 , Pg.213 , Pg.214 , Pg.215 , Pg.216 , Pg.217 , Pg.218 , Pg.219 , Pg.220 , Pg.221 , Pg.222 , Pg.223 ]

See also in sourсe #XX -- [ Pg.198 , Pg.210 , Pg.212 , Pg.213 , Pg.214 , Pg.215 , Pg.216 , Pg.217 , Pg.218 , Pg.219 , Pg.220 , Pg.221 , Pg.222 , Pg.223 ]

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