- First regioselective c-2 lithiation of 3- and 4-chloropyridines
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We have shown that the BuLi/LiDMAE reagent promotes the clean and regioselective C2 lithiation of 3- and 4-chloropyridines, while other reagents such as LDA or BuLi/TMEDA lead to classical ortho lithiation products or mixtures of regioisomers. The method was successfully applied to the preparation of various reactive 2,3- and 2,4-disubstituted pyridines.
- Choppin, Sabine,Gros, Philippe,Fort, Yves
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p. 603 - 606
(2007/10/03)
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- On the Mechanism of the Carbodesilylation of 4- or 5-Substituted 2-(Trimethylsilyl)pyridines
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An "ylide mechanism" is proposed for the carbodesilylation of 2-(trimethylsilyl)pyridines with benzaldehyde.In contrast, 3- and 4-(trimethylsilyl)pyridines, react only in the presence of a base catalyst via pyridyl anions with electrophiles.The rates of the uncatalyzed carbodesilylation reactions of 4-substituted 2-(trimethylsilyl)pyridines 2 with benzaldehyde correlate very well with the resonance parameters of the substituents ?0R, whereas the rates of 5-substituted 2-(trimethylsilyl)pyridines 7 correlate with the inductive substituent parameters ?1 in the Taft equation.This is to our knowledge the first direct determination of the resonance parameters ?0R.Key Words: Pyridines, substituted 2-(trimethylsilyl)-, synthesis of, carbodesilylation of / Carbodesilylation / Rate constants
- Effenberger, Franz,Krebs, Andreas,Willrett, Peter
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p. 1131 - 1140
(2007/10/02)
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