A hydrophilic heterogeneous cobalt catalyst for fluoride-free Hiyama, Suzuki, Heck and Hirao cross-coupling reactions in water. Issue 4 (5th February 2020)

• Record Type: Journal Article
• Authors: Sobhani, Sara; Hosseini Moghadam, Hadis; Skibsted, Jørgen; Sansano, José Miguel
• Is Part Of: Green chemistry. Volume 22:Issue 4(2020)
• Page Start: 1353
• Page End: 1365
• Publication Date: 2020-02-05
• Subjects: Environmental chemistry -- Industrial applications -- Periodicals; Environmental management -- Periodicals; 660
• DOI: 10.1039/c9gc03455b
• Languages: English
• ISSNs: 1463-9262

Abstract

Abstract : A hydrophilic chitosan-cobalt-Schiff base catalyst denoted as mTEG-CS-Co-Schiff-base was prepared for C–C and C–P cross coupling reactions in water. Abstract : A hydrophilic heterogeneous cobalt catalyst of chitosan, denoted as mTEG-CS-Co-Schiff-base, has been successfully prepared. This newly synthesized catalyst was characterized by different methods such as XRD, FE-SEM, TEM, TGA, FT-IR, 13 C{ 1 H} CP/MAS NMR, XPS and ICP analyses. The catalyst displayed excellent activity for the palladium and fluoride-free Hiyama, Suzuki, Heck and Hirao reactions of various aryl iodides, bromides and chlorides ( i.e., the most challenging aryl halides which are cheaper and more widely available than aryl iodides and bromides) in water. The presence of triethylene glycol tags with hydrophilic character on the Co-complex supported on chitosan provides dispersion of the catalyst particles in water, which leads to higher catalytic performance and also facile catalyst recovery by successive extraction. It was reused for at least six successive runs without any discernible decrease in its catalytic activity or any remarkable changes in catalyst structure. The use of water as a green solvent, without requiring any additive or organic solvent, as well as use of a low cost and abundant cobalt catalyst instead of expensive Pd catalysts along with the catalyst recovery and scalability, make this method favorable from environmental and economic points of view for the C–C and C(sp 2 )–P coupling reactions. Notably, this is the first report on the application of a cobalt catalyst in Hiyama reactions.