Stereoselective Ring Opening of Electronically Excited Cyclohexa-2, 4-dienones: Cause and effect |
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| Authors: | Gerhard Quinkert,Stefan Scherer,Dietmar Reichert,Hans-Peter Nestler,Helma Wennemers,Andreas Ebel,Klaus Urbahns,Klaus Wagner,Klaus-Peter Michaelis,Gerhard Wiech,Gü nter Prescher,Bernd Bronstert,Bernd-Jü rgen Freitag,Ilka Wicke,Dietmar Lisch,Pavel Belik,Thorsten Crecelius,Dirk H rstermann,Gottfried Zimmermann,Jan W. Bats,Gerd Dü rner,Dieter Rehm |
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| Affiliation: | Gerhard Quinkert,Stefan Scherer,Dietmar Reichert,Hans-Peter Nestler,Helma Wennemers,Andreas Ebel,Klaus Urbahns,Klaus Wagner,Klaus-Peter Michaelis,Gerhard Wiech,Günter Prescher,Bernd Bronstert,Bernd-Jürgen Freitag,Ilka Wicke,Dietmar Lisch,Pavel Belik,Thorsten Crecelius,Dirk Hörstermann,Gottfried Zimmermann,Jan W. Bats,Gerd Dürner,Dieter Rehm |
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| Abstract: | The two conformers of a cyclohexa-2, 4-dienone with different substituents at C(6) on irradiation are believed to undergo ring opening stereospecifically affording a mixture of two configurationally isomeric diene-ketenes (and descendents thereof)- Exceptions are generally found for those dienones with one C and one O substituent or even with two C substituents, if one of them carries a polar group at a site able to interact through space with the ring C?O group. In these cases, only one of the two anticipated diene-ketenes (and descendents thereof) is produced. A thorough investigation of the photochemistry of a series of structurally different cyclohexa-2, 4-dienones on analytical as well as on preparative scale extends our mechanistic knowledge of the various routes from diene-ketenes into a variety of compound classes. Novel compound classes accessible to diene-ketenes are seven-membered carbocycles (by intramolecular aldolization of the zwitterion of appropriately substituted, transiently formed diene-(N, O)-ketene acetals) and β-lactams (by Staudinger reaction). |
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