Sustainable heterogeneous catalysts for arylation of arenes via C H and C O bond activation

Title : Sustainable heterogeneous catalysts for arylation of arenes via C H and C O bond activation

Abstract:

Selective cleaving and functionalizing C-H, C-O bond in organic chemistry still remains a great challenge due to its weakest reactivity. Transition metal catalysts played a significant role in constructing various organic molecules through C-C coupling by activating the C-H and C-O bond. However, the need for ligands and additives are inevitable for homogeneous catalysts to accomplish the good yield and selectivity. On the other hand, heterogeneous catalysts do not find widespread application in organic transformations involving C-H and C-O bond activation due to its poor catalytic activity. Thus, an effective heterogeneous catalyst for challenging organic transformations besides possessing its advantages must have distinct active sites like its homogeneous counterpart. Here we show Fe and Al grafted over mesoporous silica SBA-15 as sustainable, efficient heterogeneous catalysts towards arylation of arenes. 8wt%Fe/SBA-15 has proven as efficient heterogeneous iron catalyst for direct arylation of biphenyl methane C(sp³)-H and benzene C(sp²)-H. Selective extraction deposition (SED) technique was adopted to graft iron easily over the mesoporous support SBA-15 using LaFeO₃ as an iron precursor. The adopted SED technique is highly successful to graft 8wt% iron without forming iron oxide particle into the mesopores of SBA-15. It could be successfully recycled for 5 cycles. In the same way, alumina grafted SBA-15 catalyst demonstrated excellent catalytic activity towards the construction of diarylmethane using aryl boronic acid and 2-naphthalene methanol as reactants. It was observed that the presence of Brønsted acid sites (originates by incorporation of Al in the silica framework) and Lewis acid-base sites together over the support is critical to catalyzing the above reaction with 79% isolated yield. The catalyst was successfully recycled 5 times. In another study, iron grafted over 10wt% alumina coated SBA-15 (AlSBA-15) through SED technique demonstrated excellent redox catalytic activity like homogeneous iron catalyst in arylation of benzene with 74% biphenyl yield without additives. Alumina act as a solid-state ligand to polarize the electrons of Fe(III) grafted over them through its Lewis acid property.  The catalyst performed successfully for 7 cycles.

Biography:

Dr. G. Satishkumar is an Assistant Professor (Senior) in the Department of chemistry, SAS, VIT, Vellore since 2010. He has completed M.Sc Chemistry and Ph.D at Anna University, Chennai. He was previously working as a visiting Scientist in KIST, South Korea. Latter, as a post-doctoral researcher in the Blechner center for industrial catalysis and processing, Ben-Gurion University of the Negev, Israel. His current research has focus on designing sustainable heterogeneous catalysts for various challenging organic transformation and recalcitrant pollutant degradation. He received funded projects from DST and Indo-Israel bilateral programme. He has published his research work in reputed catalysis Journals.