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Thermisches Verhalten von o ‐Dipropenylbenzol, Beispiel einer aromatischen [1,7]‐sigmatropischen H‐Verschiebung. Vorläufige Mitteilung
Author(s) -
Heimgartner[] H.,
Hansen H.J.,
Schmid H.
Publication year - 1970
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19700530124
Subject(s) - chemistry , conrotatory and disrotatory , cis–trans isomerism , isomerization , ring (chemistry) , stereochemistry , sigmatropic reaction , medicinal chemistry , catalysis , organic chemistry
cis, cis‐, cis, trans ‐ and trans, trans‐o ‐Dipropenylbenzene ( cis, cis‐, cis, trans ‐ and trans, trans ‐ 1 ) were prepared. At 225° cis, cis ‐ 1 isomerises to give cis, trans ‐ 1 and vice versa. The isomerisation follows 1. order kinetics. At equilibrium 89% cis, trans ‐ and 11% cis, cis ‐ 1 are present. It is shown by deuterium labelling that the isomerisation is due to aromatic [1, 7 a ] sigmatropic H‐shifts. trans, trans ‐ 1 rearranges at 225° to yield 2, 3‐dimethyl‐1, 2‐dihydronaphthalene ( 3 ). This can be visualized by disrotatory ring closure of trans, trans ‐ 1 followed by an aromatic [1, 5 s ] H‐shift. When cis, cis ‐ or cis, trans ‐ 1 are heated for 153 hrs at 225° a small amount (3%) of 1‐ethyl‐1,2‐dihydronaphthalene ( 5 ) is formed.