183313-44-2Relevant articles and documents
Transition-metal-free intramolecular carbene aromatic substitution/Büchner reaction: Synthesis of fluorenes and [6,5,7]benzo-fused rings
Liu, Zhenxing,Tan, Haocheng,Wang, Long,Fu, Tianren,Xia, Ying,Zhang, Yan,Wang, Jianbo
supporting information, p. 3056 - 3060 (2015/03/30)
Intramolecular aromatic substitution and Büchner reaction have been established as powerful methods for the construction of polycyclic compounds. These reactions are traditionally catalyzed by RhII catalysts with a-diazocarbonyl compounds as the substrates. Herein a transition-metal-free intramolecular aromatic substitution/Büchner reaction is presented. These reactions use readily available N-tosylhydrazones as the diazo compound precursors and show wide substrate scope.
Intramolecular reactivity of arylcarbenes: Biphenyl-2-ylcarbenes
Dorra, Michael,Gomann, Klaus,Guth, Michael,Kirmse, Wolfgang
, p. 598 - 610 (2007/10/03)
Biphenyl-2-ylcarbenes, 2-ArC6H4CR, were generated photolytically and thermally from diazo precursors. Cyclization, leading to fluorenes, competes with capture of the carbenes by methanol but proceeds faster than intramolecular hydrogen shifts (with R = Me) and intermodular C - H insertion reactions (with R = H in cyclohexane). By comparison of product ratios with kinetic data for related carbenes from the literature, the cyclization rate is estimated as ca 1011 s-1. The intramolecular reactivity of biphenyl-2-ylcarbenes is not significantly attenuated by variation of R (R = H, Me, Ph). Very minor effects of triplet sensitization and methanol quenching indicate that fluorenes arise from spin-equilibrated biphenyl-2-ylcarbenes, presumably from the singlet state. When Ar = mesityl, the carbene predominantly inserts into C - H bonds of the 2′-methyl groups, giving rise to a dihydrophenanthrene. Formation of a fluorene derivative, by formal insertion into C - C bonds, occurs as a minor process. This unprecedented reaction points to intervention of an o-xylylene in which the methyl group migrates. Laser flash photolysis (LFP) of 2-PhC6H4CN2Ph generates a transient absorption which is due to the T0→Tn transition of 9-phenylfluorene rather than to the presumed o-xylylene. On LFP of 2-ArC6H4CN2Ph in trifluoroethanol-acetonitrile, protonation of the carbenes gives rise to carbocations, 2-ArC6H4CH+Ph. The transient absorption spectra of these cations are strongly influenced by twisting about the Ar - Ar bond (Ar = Ph 4.