- Benzoquinones and Related Compounds. Part 4. Thermolysis of the Diels-Alder Adduct of 2-Acetyl-5,6-dichloro-1,4-benzoquinone and Cyclopentadiene: Evidence for a Partial Retro-diene Reaction
-
Addition of chlorine to (2-methyl-1,3-dioxolan-2-yl)-1,4-benzoquinone occurs at the unsubstituted double bond.Subsequent enolisation and cleavage of the acetal affords 2-acetyl-5,6-dichlorohydroquinone in 50percent overall yield.Oxidation of this gives the corresponding 1,4-benzoquinone which with cyclopentadiene yields, predominantly, the 1 : 1 Diels-Alder adduct (6) by endo-addition to the 2,3-double bond.Thermolysis of this adduct in benzene results in disproportionation to cyclopentadiene and the spiro-acetal (13); thermolysis in acetic acid also yields (13), but the major product is the dihydrobenzofuran (14), an isomer of the Diels-Alder adduct.Mechanisms for the formation of these products are discussed.
- Beddoes, Roy L.,Bruce, J. Malcolm,Finch, Harry,Heelam, Leslie M. J.,Hunt, Ian D.,Mills, Owen S.
-
p. 2670 - 2676
(2007/10/02)
-