Y. Cui, H. Jiang, Z. T. Li, N. Wu, Z. Yang* and J. M. Quan*
Org. Lett. 2009, 11, 4628.
The unusual regioselectivity in the Diels−Alder reactions of pyranoquinone 1 with (4,4-dimethoxybuta-1,3-dien-2-yloxy)trimethylsilane 2 are explored by both computations and experiments. The regioselectivity is controlled by the electrostatic interaction of the lactone ring-oxygen and the vicinal quinone oxygen on the transition structure, which can be tuned by the terminal methyl group of the butadienes.
