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Stereoselective Ring Opening of Electronically Excited Cyclohexa‐2, 4‐dienones: Cause and effect
Author(s) -
Quinkert Gerhard,
Scherer Stefan,
Reichert Dietmar,
Nestler HansPeter,
Wennemers Helma,
Ebel Andreas,
Urbahns Klaus,
Wagner Klaus,
Michaelis KlausPeter,
Wiech Gerhard,
Prescher Günter,
Bronstert Bernd,
Freitag BerndJürgen,
Wicke Ilka,
Lisch Dietmar,
Belik Pavel,
Crecelius Thorsten,
Hörstermann Dirk,
Zimmermann Gottfried,
Bats Jan W.,
Dürner Gerd,
Rehm Dieter
Publication year - 1997
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.19970800602
Subject(s) - chemistry , zwitterion , substituent , ring (chemistry) , intramolecular force , diene , ketene , stereoselectivity , stereochemistry , conformational isomerism , stereocenter , medicinal chemistry , molecule , organic chemistry , catalysis , enantioselective synthesis , natural rubber
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 CO 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).