- Pd- and Ni-catalyzed cross-coupling reactions of functionalized organozinc reagents with unsaturated thioethers
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A variety of unsaturated thioethers have been subjected to cross-coupling reactions with functionalized zinc reagents in the presence of a transition-metal catalyst. Three different catalytic systems based on Pd(OAc)2 or [Ni(acac)2] and the ligands S-Phos or DPE-Phos gave the best results. N-Heterocyclic thioethers based on a pyridine, pyrimidine, pyrazine, pyridazine, triazine, benzothiazole, benzoxazole, pyrrole, or quinazoline ring, as well as thiomethylacetylenes, serve as electrophiles in this cross-coupling reaction. Aryl-, heteroaryl-, benzylic, and alkylzinc halides with sensitive functionalities, such as ester, nitrile, or ketone groups react at ambient temperature with unsaturated thioethers using a Ni catalyst. The corresponding Pd-catalyzed reactions require slightly higher temperatures. Large-scale cross-coupling experiments (10-20 mmol) with N-heterocycles are also reported.
- Melzig, Laurin,Metzger, Albrecht,Knochel, Paul
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supporting information; experimental part
p. 2948 - 2956
(2011/04/16)
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- Scaled-up transition-metal-catalyzed cross-coupling reactions of thioether-substituted N-heterocycles with organozinc reagents
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A variety of functionalized methylthio-substituted N-heterocycles (pyridines, pyrimidines, pyrazines, pyridazines, triazines, quinazolines, benzothiazoles) undergo smooth palladium- or nickel-catalyzed cross-couplings with highly functionalized organozinc reagents at ambient temperature. No expensive copper(I) salts are required and the coupling reactions proceed readily in the range of up to 20 mmol scale. Georg Thieme Verlag Stuttgart.
- Metzger, Albrecht,Melzig, Laurin,Knochel, Paul
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experimental part
p. 2853 - 2858
(2010/10/03)
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- An unusual reaction of benzalaminoacetals in trifluoroacetic acid: Facile synthesis of 2-benzylpyrazines
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(Chemical Equation Presented) Benzalaminoacetals (1), upon refluxing with trifluoroacetic acid, lead to 2-benzylpyrazines, rather than the expected isoquinolines. This unusual reaction represents another useful way to prepare a variety of 2-benzylpyrazines from the corresponding benzaldehydes.
- Augustine, John Kallikat,Naik, Yanjerappa Arthoba,Mandal, Ashis Baran,Kundapur, Umesha
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p. 1176 - 1179
(2008/09/18)
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