1. Palladium-catalyzed Suzuki–Miyaura cross-coupling with $\alpha $-aminophosphonates based on 1,3,4-oxadiazole as ligands
- Author
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Hkiri, Shaima, Touil, Soufiane, Samarat, Ali, and Sémeril, David
- Subjects
$\alpha $-Aminophosphonate ,1,3,4-Oxadiazole ,Palladium catalysis ,Suzuki–Miyaura cross-coupling ,Hemilabile ligand ,Biochemistry ,QD415-436 ,Physical and theoretical chemistry ,QD450-801 ,Mathematics ,QA1-939 - Abstract
The synthesis of a palladium complex bearing two diethyl[(5-phenyl-1,3,4-oxadiazol-2-ylamino)(4-nitrophenyl)methyl]phosphonates as ligands has demonstrated the ability of this type of $\alpha $-aminophosphonates to coordinate to the palladium(II) ion via their electronically enriched nitrogen atom of the 1,3,4-oxadiazole ring. The complex was fully characterized by elemental analysis, infrared, NMR and mass spectrometry. A solid-state structure revealed the trans coordination of the two nitrogenated ligands. The presence of a hemilabile P(O)(OEt)$_{2}$ moiety in the $\alpha $-aminophosphonates was exploited into palladium-catalyzed Suzuki–Miyaura cross-coupling of aryl halides. The formation of ($N{,}O$)-chelate intermediates may increase the steric hindrance and the electronic density of the metal, which should favor the oxidative addition and the reductive elimination/product decoordination elementary steps. With our catalytic systems, good activities for the formation of ortho-di/trisubstituted biphenyl compounds were observed from aryl bromides using only 0.5 mol% of palladium. Cross-coupling of aryl chlorides required a catalyst loading of 1 mol% to generate ortho-substituted biphenyls.
- Published
- 2022
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