Kopach, M. E.; Harman, W. D. The Osmium-Promoted [4+2] Cycloaddition Reaction of Anisole and Characterization of the η2-4H-Anisolium Intermediate. Journal of Organic Chemistry 1994, 59, 6506-6507.
Abstract
Summary: Anisóle, when complexed by pentaammin-
eosmium(II), undergoes a [4 + 2] cycloaddition with
N-methylmaleimide which is shown to be nonconcerted.
