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The Photoisomerization of 1,2,3,4,5‐Pentamethyl‐5‐vinyl‐1,3‐cyclopentadiene
Author(s) -
Burger Ulrich,
Etienne Robert
Publication year - 1984
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.19840670805
Subject(s) - chemistry , cyclopentadiene , photoisomerization , bicyclic molecule , photodissociation , photochemistry , acetophenone , irradiation , derivative (finance) , deuterium , isomerization , medicinal chemistry , organic chemistry , nuclear physics , financial economics , economics , catalysis , physics , quantum mechanics
The title compound 1 is shown to give, both upon direct irradiation at 254 nm and upon acetophenone‐sensitized photolysis at 300 nm, the syn ‐vinyl‐pentamethylhousene 5 , which spontaneously rearranges in a [3,3]0sigmatropic process to give the bicyclo[3.2.0]heptadiene skeleton 2 . Based on the photochemical behaviour of selectively deuterated starting material, the suggestion is made that the direct photolysis produces the vinylhousene skeleton by a classic electrocyclization, whereas the sensitized reaction reaches the same target via a di‐π‐methane rearrangement. The bicyclo[3.2.0]heptadiene derivative 2 give pentamethylhomoprismane 3 upon prolonged irradiation at 254 nm.