Periselectivity and ambimodal transition states in cycloadditions of tetrachloro‐o‐benzoquinone with 6,6‐dimethylfulvene.

The reaction mechanism of cycloadditions of tetrachloro‐o‐benzoquinone with 6,6‐dimethylfulvene were systematically investigated with density functional theory calculations. It was found that conditional primary interactions stabilize the ambimodal transition states in the endo pathways. Ambimodal transition states lead to [6 + 4]/[4 + 2] adducts or [4 + 2]/[2 + 4] adducts, which interconvert through 3,3‐sigmatropic shift reactions. The substituent effects on periselectivity were also investigated. [ABSTRACT FROM AUTHOR]