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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 21, Number 2
BKCSDE 21(2)
February 20, 2000 

 
Title
Dehalogenation of Monohalopyridines Catalyzed by Group 4 Metallocene Reagent
Author
Bo-Hye Kim, Hee-Gweon Woo, Whan-Gi Kim, Sock-Sung Yun, Taek-Sung Hwang
Keywords
Abstract
The Cp'2MCl2/hydride (Cp' = Cp or Cp * : Cp = η5 -C5H5, Cp * = η5 -C5Me5; M = Ti, Zr, Hf) reagent catalyzes the dehalogenation of monohalopyridines at room temperature to give pyridine. The catalytic activity decreases in the order of M = Ti > Zr > Hf: M-F ∼ M-Cl ∼ M-Br ∼ M-I; Cp2M > CpCp * M>Cp * 2M; Red-Al > N-Selectride > K-Selectride > L-Selectride >> DIBAL-H, MeLi, n-BuLi; 2-fluoropyridine > 3-fluoropyridine; C-F > C-Cl > C-Br. The rate of dehalogenation is boosted by adding 4 Å molecular sieve. The catalyst combinations are all ineffective on the defluorination of fluorobenzenes and perfluorodecalin at the reaction condition. The pos-sible mechanisms are suggested.
Page
211 - 214
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