Photochemical studies—XXI : Dimers of 3,4-(o,o'-biphenylene)cyclopentadienones: Thermal and photochemical behaviour

The 1,4-dimethyl-, 1,2,4-trimethyl and 1,2,4,7-tetramethyl substituted 3,4-(o,o'-biphenylene) cyclopentadienone-dimers (6a–6c) were prepared and found to undergo photochemically or thermally a 1,3-rearrangement to the centrosymmetrical diketones (11). Only the tetramethyl derivative (6a) undergoes at room temperature a fast, degenerate [3.3] Cope rearrangement with ΔG^≠₂₃₃ = 11.4 kcal mol.^?1 All these dimers and rearrangement products appear not to dissociate to their monomers, but react with dienophiles to give the adducts (12, 13). A stepwise mechanism involving diradical intermediates (19) is invoked. The “mixed dimer” (14) was also prepared and studied. The steric and electronic effects determining the behaviour of these compounds are discussed.     

Wann folgt die Maximalbedingung aus der Minimalbedingung?

Ohne Zusammenfassung     

Kinetik physikalisch-chemischer Oszillationen

Ohne Zusammenfassung     

Prozesse an organisierten molekularen Systemen: Monomolekulare Schichten,Mizellen, Bilayer-Membranen

Ohne Zusammenfassung     

Buchbesprechungen

Ohne Zusammenfassung