90266-01-6Relevant articles and documents
Dynamic equilibria in the products of intramolecular buchner additions of diazoketones to aryl rings bearing methoxy substituents
Maguire,O'Leary,Harrington,Lawrence,Blake
, p. 7166 - 7177 (2007/10/03)
Rhodium carboxylate catalyzed aromatic addition reactions of a range of diazoketones bearing methoxy-substituted aryl rings have been explored. While the existence of norcaradiene-cycloheptatriene equilibria in related compounds is well established, the aromatic addition products in this study display more complex dynamic equilibria due to conjugation with the methoxy group; the experimental evidence for this is discussed in detail. In the azulenone products 21-26 derived from p-methoxy-substituted diazoketones 14-16, the diastereomers interconvert via a spiro intermediate 39. A related mechanistic process in the azulenones 43-46 derived from the o-methoxy-substituted diazoketones 17, 18 interconverts regioisomers, explaining the conflicting reports for the regioselectivity of the cyclization of diazoketone 1. With the m-methoxy-substituted diazoketone 19, involvement of the methoxy group through a different pathway results in fragmentation of the azulenone to form the tetralone 47. With the azulenones 21-26 exclusive trapping of the norcaradiene associated with the less thermodynamically stable diastereomers in a cycloadduct with N-phenylmaleimide is observed. Due to the presence of the activating methoxy substituent on the aromatic ring, the aromatic addition reactions of the diazoketones studied were not very sensitive to the nature of the rhodium catalyst.
The Intramolecular Buchner Reaction of Aryl Diazoketones. Substituent Effects and Scope in Synthesis
Kennedy, Michael,McKervey, M. Anthony,Maguire, Anita R.,Tuladhar, Sarbajna M.,Twohig, M. Fiona
, p. 1047 - 1054 (2007/10/02)
Rhodium(II) acetate-catalysed cyclisation of α-diazoketones derived from 3-arylpropionic acid produces bicyclodecatrienones or 2-tetralones depending on the substitution pattern of the aryl ring in the precursor; the former products are transformed into the latter catalytically with trifluoroacetic acid.Precursors with methyl, methoxy, and acetoxy substituents have been examined, efficient cyclisation occurring in all cases.When the precursor contains a meta-methoxy substituent, 2-tetralones are obtained directly.The efficient conversion of 3-phenylpropionicacid into trans-1-methylbicyclodecan-2-one is also described, partial asymmetric synthesis having been realised through the use of rhodium (S)-mandelate as the cyclisation catalyst.Cyclisations of diazoketones derived from 4-phenylbutyric acid and 5-phenylpentanoic acid have also been studied; the former provides a new entry into the bicycloundecane system whereas the latter produces a 2,3-disubstituted cyclopentanone via C-H insertion.Aspects of the cycloheptatriene-norcaradiene equilibrium in fused ring systems are discussed.
Efficient Synthesis of Bicyclodecatrienones and of 2-Tetralones via Rhodium(II) Acetate-catalysed Cyclisation of α-Diazoketones derived from 3-Arylpropionic Acids
McKervey, M. Anthony,Tuladhar, Sarbajna M.,Twohig, M. Fiona
, p. 129 - 130 (2007/10/02)
Rhodium(II) acetate-catalysed cyclisation of α-diazoketones derived from 3-arylpropionic acids produces bicyclodecatrienones or 2-tetralones depending on the substitution pattern of the aryl ring; the former products are transformed into the latter by catalytic amounts of trifluoroacetic acid.
