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A Stable N-Heterocyclic Carbene Organocatalyst for Hydrogen/Deuterium Exchange Reactions between Pseudo-acids and Deuterated Chloroform

Abstract : It was observed that the stable and commercially 
available N-heterocyclic carbene (NHC) 1,3-bis(2,6-diisopropyl-
phenyl)imidazol-2-ylidene, the so-called IDipp, catalyzes hydrogen/
deuterium exchange reactions between pseudoacids and chloroform-
d1, while the analogous saturated NHC 1,3-bis(2,4,6-trimethyl-
phenyl)imidazolin-2-ylidene, the so-called SIMes, is inefficient for the same transformation. Experimental and computational DFT
studies allowed these differences of reactivity to be attributed to the 
relative stability of the corresponding azolium−trichloromethyl anion ion pairs: in the former case, the complex evolves toward dissociation of the ions to produce an aromatic azolium cation and a basic trichloromethyl anion, while in the latter case, it evolves by ion recombination to give the product of formal carbene C−H insertion into the C−H bond of chloroform. These results provide a rationale for some early intuitions and observations of Wanzlick, Arduengo, and others on the reactivity of NHCs with chloroform as well as a simple organocatalytic method for the deuteration of pseudoacids (pKa,DMSO = 14−19) with chloroform-d1.
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https://hal.archives-ouvertes.fr/hal-01133529
Contributor : Gaelle Chouraqui Connect in order to contact the contributor
Submitted on : Thursday, March 19, 2015 - 3:42:18 PM
Last modification on : Tuesday, December 14, 2021 - 8:36:12 AM

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Fabien Perez, Yajun Ren, Thomas Boddaert, Jean Rodriguez, Yoann Coquerel. A Stable N-Heterocyclic Carbene Organocatalyst for Hydrogen/Deuterium Exchange Reactions between Pseudo-acids and Deuterated Chloroform. Journal of Organic Chemistry, American Chemical Society, 2015, 80, pp.1092-1097. ⟨10.1021/jo502578x⟩. ⟨hal-01133529⟩

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