Mechanistic Investigations of the Acid‐Catalyzed Cyclization of a Vinyl <i>ortho</i>‐Quinone Methide

Abstract

Acid-catalyzed and thermal cyclization of an isolable vinyl ortho-quinone methide has been kinetically and computationally investigated. We propose that both reactions proceed through rate-limiting exo-alkylidene bond isomerization followed by faster oxa-6π electrocyclization. The vinyl ortho-quinone methide was found to be surprisingly basic, allowing for quantitative protonation with relatively weak acids. In addition, we have identified a new mode of Diels–Alder dimerization of vinyl ortho-quinone methides. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2111/2008/z800662_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.