- Cheap and easy synthesis of highly functionalized (het)aryl iodides via the aromatic finkelstein reaction
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Aryl iodides are superior coupling partners in cross-couplingA- reactions compared to the corresponding chlorides or bromides. Unfortunately, the iodides are much more expensive, if commercially available at all, than the other halides. Thus, it is often mandatory to transform the available bromides into the corresponding iodides. The copper-catalyzed aromatic Finkelstein reaction turned out to be the method of choice to prepare a number of highly functionalized iodo(het)aryls, including pyridines, 2,2′-bipyridines, and chiral compounds. Georg Thieme Verlag Stuttgart? New York.
- Meyer-Eppler, Georg,Kuechler, Lea,Tenten, Christina,Benkhaeuser, Christian,Brueck, Stefanie,Luetzen, Arne
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p. 1085 - 1090
(2014/05/06)
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- Homoleptic zincate-promoted room-temperature halogen-metal exchange of bromopyridines
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Homoleptic lithium tri- and tetraalkyl zincates were reacted with a set of bromopyridines. Efficient and chemoselective bromine-metal exchanges were realized at room temperature with a substoichiometric amount of nBu 4ZnLi2·TMEDA reagent (1/3 equiv; TMEDA=N,N,N′,N′-tetramethylethylenediamine). This reactivity contrasted with that of tBu4ZnLi2·TMEDA, which was inefficient below one equivalent. DFT calculations allowed us to rationalize the formation of N...Li stabilized polypyridyl zincates in the reaction. The one-pot difunctionalization of dibromopyridines was also realized using the reagent stoichiometrically. The direct creation of C-Zn bonds in bromopyridines enabled us to perform efficient Negishi-type cross-couplings. Mild zincation! nBu4ZnLi2·TMEDA (in substoichiometric amounts) promoted efficient and chemoselective room-temperature bromine-metal exchange of a range of bromopyridines (see scheme). DFT calculations strongly supported the formation of a stabilized tripyridylzincate, which could be reacted with electrophiles or be directly involved in palladium-catalyzed cross-coupling reactions.
- Chau, Nguyet Trang Thanh,Meyer, Maxime,Komagawa, Shinsuke,Chevallier, Floris,Fort, Yves,Uchiyama, Masanobu,Mongin, Florence,Gros, Philippe C.
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experimental part
p. 12425 - 12433
(2011/01/05)
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