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Synthesis of Methylene‐Bridge Polyarenes through Palladium‐Catalyzed Activation of Benzylic Carbon‐Hydrogen Bond
Author(s) -
Hsiao ChienChi,
Lin YiKuan,
Liu ChiaJu,
Wu TsunCheng,
Wu YaoTing
Publication year - 2010
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201000651
Subject(s) - chemistry , diphenylacetylene , medicinal chemistry , palladium , carbene , aryl , catalysis , fluorene , alkyne , methylene bridge , nitrile , alkyl , organic chemistry , polymer
In the presence of palladium(II) acetate [Pd(OAc) 2 ] and an N‐heterocyclic carbene (NHC) ligand, fluorene derivatives can be generated in good to excellent yields from 2‐halo‐2′‐methylbiaryls through the benzylic CH bond activation (14 examples; 81–97% yields). The scope and limitations of this protocol have been examined. A wide range of functional groups, such as alkyl, alkoxy, ester, nitrile, and others, is able to tolerate the reaction conditions herein. The cyclization of an isotope‐labelled biphenyl gave the corresponding product with a primary kinetic isotope effect ( k H / k D =4.8:1), which indicates that the rate‐determining step of this reaction is the activation of the benzylic CH bond. Moreover, indenofluorenes were also accessed in excellent results from terphenyls (3 examples; 91–92% yields). The cascade reaction of 2,6‐dichloro‐2′‐methylbiphenyl with diphenylacetylene produced 8,9‐diphenyl‐4 H ‐cyclopenta[ def ]phenanthrene in 60% yield through the activation of an aryl and a benzylic CH bond.