76374-17-9Relevant articles and documents
The Photochemical Reactions of Benzene with 1,2-, 1,3-, and 1,4-Dienes
Berridge, John C.,Forrester, John,Foulger, Brian E.,Gilbert, Andrew
, p. 2425 - 2434 (1980)
The photocycloaddition reactions of benzene with 1,2-, 1,3-, and 1,4-dienes are described.Propa-1,2-diene (allene) and cyclonona-1,2-diene are unique among hydrocarbon ethylenic systems since 1,2-para-cycloaddition to the benzene ring is the major mode of reaction.The meta-cycloaddition of 1,2-dienes is regiospecific and this is accounted for by a mechanism involving prior meta-bonding in the arene leading to a polarised prefulvene species which undergoes 1,2-addition to the diene.The conformationally fixed cis-diene 1,2-dimethylenecyclohexane undergoes selective 1,4-para and 1,4-meta-photocycloaddition to benzene whereas the reaction with 3-methylenecyclohexene is of low yield and non-selective giving diene dimers, substitution products, and adducts.Penta-1,4-diene and cyclohexa-1,4-diene yield 1,2-meta-cyclo-adducts with benzene, and evidence is presented for formation of 1,2-para-cycloadducts from each system: diene dimers are also produced in the latter case but solutions of bicyclohepta-2,5-diene in benzene are essentially inert photochemically.
