[4+2] Cycloadditions of cyclopentadienes 1a-1i with aryl-substituted c
yclic and open-chain dienophiles usually gave single endo-cycloadducts
in high yield. Assignment of the product structures involved H-1-NMR
spectroscopy including (H-1,H-1) long-range coupling and (H-1,F-19) th
rough-bond and through-space coupling.