Irradiation carbon skeleton rearrangements

Irradiation of an acetonitrile solution of octafluoronorbornadiene with a full medium-pressure mercury arc rearranged the carbon skeleton, yielding first octafluorotricyclo[3.2.0.02-7]hept-3-ene and then, on continued irradiation, perfluorobicyclo[3.2.0]hepta-2,6-diene (35).105... 

The DPM rearrangement has provided a simple route for the construction of the carbon skeleton present in the sesquiterpenoid taylorione, isolated from Mylia taylori [46]. Thus, direct irradiation of the i>cyclopentenone 62 results in efficient, regiospecific DPM reaction affording the r[Pg.177]

Ultraviolet irradiation causes changes in carbon skeleton of many compounds. A classical example is conversion of hexafluorobenzene to hexafluoro Dewar benzene [759], and isomerization of benzene to three isomers. The same is true of hexakis(trifluoromethyl)benzene, which rearranges to the perfluorinated isomers of hexamethyl Dewar benzene (F), prismane (G), and benzvalene (H) [140]. 

An elegant example of the use of the Favorskii rearrangement was in the first deliberate synthesis of the cubane carbon skeleton in 1964 by Eaton and Cole. " Their sequence begins with 2-cyclopentenone 10, which is first mono-brominated with NBS and then di-brominated using Br2 to give 11. Double dehydrobromination is achieved using diethylamine to form transient species 12, which immediately self-dimerizes via a Diels-Alder reaction to form 13. Subsequent ultraviolet light irradiation in the presence of HCl... 

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