Homoleptic Zincate‐Promoted Room‐Temperature Halogen–Metal Exchange of Bromopyridines |
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| Authors: | Dr Nguyet Trang Thanh Chau Maxime Meyer Dr Shinsuke Komagawa Dr Floris Chevallier Prof Yves Fort Prof Masanobu Uchiyama Prof Florence Mongin Dr Philippe C Gros |
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| Institution: | 1. SOR, SRSMC, Nancy Université, CNRS, Boulevard des Aiguillettes, 54506 Vandoeuvre‐Lès‐Nancy (France), Fax: (+33)?38‐3684785;2. Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7‐3‐1 Hongo, Bunkyo‐ku, Tokyo 113‐0033 (Japan);3. Chimie et Photonique Moléculaires, UMR 6510 CNRS, Université de Rennes 1, Batiment 10?A, Case 1003, Campus Scientifique de Beaulieu, 35042 Rennes Cedex (France) |
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| Abstract: | 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 nBu4ZnLi2?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. |
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| Keywords: | bromopyridines cross‐coupling halogen– metal exchange lithium zinc |
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