Journal
JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL
Volume 393, Issue -, Pages 191-209Publisher
ELSEVIER
DOI: 10.1016/j.molcata.2014.06.012
Keywords
Hydrodehalogenation; Reduction; Haloheterocycles; Palladium catalysts; Sodium borohydride; N,N,N ',N '-tetramethylethylenediamine
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Funding
- University of Sassari
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The pair NaBH4-TMEDA as hydride source and a palladium catalyst in THF prove to be an efficient system for the hydrodehalogenation of halogenated heterocycles with one or more heteroatoms. In general, Pd(OAc)(2)-PPh3 rapidly hydrodehalogenates reactive halo-heterocycles such as bromo-pyridines, -quinolines, -thiophenes, -indoles, -imidazoles, etc., at room temperature in very good yields, whereas in most cases PdCl2(dppf) reduces less reactive halides such as chloro-pyridines, -quinolines, -pyrimidines and bromo-indoles, -benzofurans, etc. Moreover, PdCl2(tbpf) shows to be even more active removing the 2- and 5-chlorine from both thiophene and thiazole rings. The reaction conditions tolerate various functional groups, allowing highly chemoselective reactions in the presence of halide, ester, alkyne, alkene and nitrile substituents. Moreover, with a proper selection of the catalyst it is also possible to obtain a good control in the regioselective hydrodehalogenation of a variety of polyhalogenated substrates. (C) 2014 Elsevier B.V. All rights reserved.
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