Synthesis and Characterization of Some Transition Metal Complexes for Homocoupling of Grignard Reagents

Abstract

The biaryl motif plays a significant role in the multidisciplinary fields ranging from natural product synthesis to supramolecular chemistry. Transition metal catalyzed homocoupling reaction is one of the powerful tools for the synthesis of symmetrical biaryls. Though, modern methods of oxidative homocoupling reactions have successively focused on the development of high-yielding reactions, establishing a more efficient catalytic routes where the same outcome is accomplished, but reactions with - reduced waste, in fewer steps, under mild reaction conditions and minimum catalyst loading - is still a challenge. In this thesis, we have discussed about the development of a catalytic methodology for the homocoupling of Grignard reagents to synthesis symmetrical biaryls in a single step. The ruthenium, palladium, cobalt, nickel and copper complexes were synthesized using dmit (2-thioxo-1,3-dithiole-4,5 dithiolate), ON and ONO Schiff bases and triphenylphosphine ligands. The synthesized complexes catalyzed the reaction effectively at room temperature. In the present study, Grignard reagents were synthesized in situ which avoids all the synthetic difficulties regarding isolation of Grignard reagents. The reaction system utilized atmospheric oxygen as a green oxidant, making the system environmentally friendly. The reaction is compatible with diverse functionalities. This study also focuses on the large impact of electronic properties of ancillary and reactive ligands on the yield and scope of homocoupling reaction. The operational simplicity, minimum byproduct, low catalyst loading, usage of green oxidant, mild reaction conditions, tolerant for diverse functionalities, higher yield and chemoselectivity makes the present catalytic system synthetically attractive for the large scale synthesis of symmetrical biaryls.