AuI-Catalyzed Hydroalkynylation of Haloalkynes
Pedro D. García-Fernández, Javier Iglesias-Sigüenza, Paula S. Rivero-Jerez, Elena Díez*, Enrique Gómez-Bengoa*, Rosario Fernández* and José M. Lassaletta*
*Universidad de Sevilla, Sevilla 41012; Universidad del Paı́s Vasco, San Sebastián 20080 Spain,
Email: ediezus.es, enrique.gomez
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P. D. García-Fernández, J. Iglesias-Sigüenza, P. S. Rivero-Jerez, E. Díez, E. Gómez-Bengoa, R. Fernández, J. M. Lassaletta, J. Am. Chem. Soc., 2020, 142, 16082-16089.
DOI: 10.1021/jacs.0c07951
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Abstract
Cationic Au complexes containing strongly basic NHC ligands and noncoordinating anions such as BArF4 catalyze a cis haloalkynylation between terminal alkynes and aromatic haloalkynes, whereas introduction of a weakly basic triflate counteranion results in the stereoselective hydroalkynylation of the haloalkyne, yielding haloenyne products in good yields and complete trans selectivity.
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Details
The article discusses the AuI-catalyzed hydroalkynylation of haloalkynes, focusing on the reaction between terminal alkynes and aromatic haloalkynes. The reaction pathways diverge based on the catalyst counteranion. Cationic complexes with strongly basic NHC ligands and noncoordinating anions like BArF4 catalyze cis haloalkynylation, while weakly basic triflate counteranions result in stereoselective hydroalkynylation, yielding trans haloenyne products. Experimental and computational studies suggest that the hydroalkynylation involves nucleophilic attack on the C2 carbon of the activated haloalkyne, assisted by concerted proton abstraction by the triflate, with protodeauration as the turnover-limiting step. The study highlights the importance of the counteranion in determining the reaction outcome and provides detailed mechanistic insights supported by kinetic isotope effects and computational analysis. The findings offer a new method for synthesizing functionalized alkynes, expanding the utility of haloalkynes in organic synthesis. The research was supported by various Spanish and European grants and involved contributions from multiple authors affiliated with Spanish universities and research centers.
Key Words
ID: J48-Y2020