- Palladium-catalyzed cross-coupling of five-membered heterocyclic silanolates
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(Chemical Equation Presented) The preparation of π-rich 2-aryl heterocycles by palladium-catalyzed cross-coupling of sodium heteroarylsilanolates with aryl iodides, bromides, and chlorides is described. The cross-coupling process was developed through extensive optimization of the following key variables: (1) identification of stable, isolable alkali metal silanolates, (2) identification of conditions for preformation and isolation of silanolate salts, (3) judicious choice in the palladium catalyst/ligand combination, and (4) selection of the protecting group on the nitrogen of indole. It was found that the alkali metal silanolates, either isolated or formed in situ, offered a significant rate enhancement and broader substrate scope over the use of silanols activated by Bronsted bases such as NaOt-Bu. In addition, the optimized conditions for the cross-coupling of 2-indolylsilanolates were readily applied to the cross-coupling of 2-pyrrolyl-, 2-furyl-, and 2-thienylsilanolates.
- Denmark, Scott E.,Baird, John D.,Regens, Christopher S.
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p. 1440 - 1455
(2008/04/12)
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- Palladium-catalyzed cross-coupling reactions of heterocyclic silanolates with substituted aryl iodides and bromides
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Sodium silanolates derived from a number of heterocyclic silanols undergo cross-coupling with a variety of aromatic iodides and bromides under mild conditions. In situ deprotonation of the silanols with an equivalent amount of sodium hydride in toluene ge
- Denmark, Scott E.,Baird, John D.
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p. 793 - 795
(2007/10/03)
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