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Verbotene Reaktionen, II Die disrotative Cyclobuten‐Ringöffnung
Author(s) -
Roth Wolfgang R.,
Rekowski Volker,
Börner Sabine,
Quast Michael
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960317
Subject(s) - conrotatory and disrotatory , cyclobutene , chemistry , isomerization , bicyclic molecule , ring (chemistry) , benzocyclobutene , photochemistry , stereochemistry , organic chemistry , polymer , catalysis
Forbidden Reactions, II. – The Disrotatory Cyclobutene Ringopening The energy profiles for the con‐ and disrotatory opening of benzocyclobutene, methylenecyclobutene, and cyclobutene derivatives were established by NO and oxygen trapping. The enthalpy for the transition states for the forbidden reactions proved to be identical with the heat of formation of the orthogonal diradicals derived by geometrical isomerization of the dienes formed in these reactions. These diradicals describe very well the activation barriers observed for the disrotatory opening of bicyclic cyclobutenes ([3.2.0] and [2.2.0] systems), but not for bicyclo[2.1.0]pent‐2‐ene, indicating here a truly forbidden reaction.