81522-28-3Relevant articles and documents
Intramolecular Reactivity of Arylcarbenes: Derivatives of o-Tolylcarbene
Kirmse, Wolfgang,Konrad, Wolfgang,Schnitzler, Dirk
, p. 3821 - 3829 (2007/10/02)
Various CH2X groups have been attached to the ortho position of phenylcarbene.If 2'- or 3'-C-H bonds are present, as in 23 (X = Me), 71 (X = CMe3), and 58 (X = SiMe3), C-H insertion leading to five- or six-membered rings predominates in the gas phase and competes with intermolecular reactions in solution.The formation of benzocyclobutenes via insertion into 1'-C-H bonds is a very minor reaction path of 23 and 71.In contrast, 58 produces substantial amounts of the benzocyclobutene 59 by way of C-Si insertion, particularly in the gas phase.Insertion into the Si-Me bonds of 58 also occurs while the C-F bonds of 37 (X = CF3) and 50 (X = F) are inert.In the gas phase, 37 and 50 give mainly benzocyclobutenes whereas intermolecular reactions prevail in solution.The effects of sensitization and of solvent polarity suggest that benzocyclobutenes arise from singlet arylcarbenes.The amount of carbene-carbene rearrangement decreases in the order 7 (X = H) > 37 (X = CF3) > 23 (X = Me); no rearrangement was observed with 50 (X = F), 58 (X = SiMe3), and 71 (X = CMe3).
Intramolekulare Einschiebung von Arylcarbenen in C-Si-Bindungen
Kirmse, Wolfgang,Konrad, Wolfgang
, p. 682 - 683 (2007/10/02)
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A New Approach to Asymmetric Synthesis of Polycycles on the Basis of o-Quinodimethane Generation
Ito, Yoshihiko,Amino, Yusuke,Nakatsuka, Masashi,Saegusa, Takeo
, p. 1586 - 1590 (2007/10/02)
The fluoride anion induced 1,4-elimination of 2-phenyl>-3,3-dimethyloxazolidinium salts generates (E,E)-α-alkyl-α'--o-quinodimethane intermediates, which are trapped stereoselectively with dienophiles to give polycycles.Intramolecular cyclization of 2-phenyl>-3,3-dimethyl-4-(R)-methyl-5(R)-phenyloxazolidinium triflate at 0 deg C produces a 3:1 diastereoisomeric mixture of 6--trans-octahydrophenanthrene, which is converted by hydrogenolysis on Pd/C to trans-octahydrophenanthrene with D +46.6 deg (50percent ee).Similarly, intramolecular cyclization of 2-phenyl>-3,3-dimethyl-4(S)-methoxymethyl-5(S)-phenyloxazolidinium triflate produces, after hydrogenolysis on Pd/C, trans-octahydrophenanthrene with D -51.1 deg (55percent ee).The enantioselection in the cycloaddition with o-quinodimethane intermediate may be accounted for on the basis of ?-stacking interaction in the Diels-Alder transition state.
