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Mechanistic Investigations of the Acid‐Catalyzed Cyclization of a Vinyl ortho ‐Quinone Methide
Author(s) -
Bishop Lee M.,
Winkler Michael,
Houk Kendall N.,
Bergman Robert G.,
Trauner Dirk
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200800662
Subject(s) - quinone methide , isomerization , protonation , chemistry , quinone , catalysis , limiting , organic chemistry , photochemistry , mechanical engineering , ion , engineering
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.