Exploration of palladium complexes of 2-arylquinolines for catalytic non-chelation-assisted direct arene C-H amination with phthalimide and iodination using inorganic iodide as reagents

Abstract

The concept of step-economical and environmentally friendly synthesis has aroused great interest in recent years. Diminishing functional group manipulations typically required to afford pre-oxidized compounds is one of the unsophisticated ways to reduce numbers of steps of a certain synthetic route via direct functionalization from targeted C-H bond to desired carbon-carbon (C-C) or carbon-heteroatom bond (C-X). Meanwhile, the selectivity issue always remains an essential obstacle in this chemistry. Generally, several types of unique C-H bonds can be found even in a moderately simple organic compound. Therefore, selective functionalization of a targeted robust C-H bond is challenging when dealing with a direct C-H bond activation based synthesis. Aryl amine is an important scaffold in medicine, agroscience and material science that makes them valuable synthetic targets, therefore, synthetic reactions that constructing C-N bonds are extensively investigated. In this thesis, we have successfully demonstrated the non-chelation-assisted arene C-H amidation with phthalimide employing palladium complexes. We began by treating simple non-directing arene (1 ml) with phthalimide (0.2 mmol) with diacetoxy iodobenzene (6.0 equiv) as the oxidant in the presence of palladium(II) acetate (5 mol%). Under the optimized reaction conditions, a wide scope of simple non-directing arenes can be amidated in good yields (50-80%) while showing good functional group tolerance. In addition, single-crystal X-ray crystallography of the [Pd(qin)(OAc)]2 complex was established. Aryl halides are essential and versatile starting materials for Grignard reaction and also numerous cross-coupling reactions that are employed for synthesizing various pharmaceuticals, natural products and functional compounds. In this thesis, we have also established the non-chelation-assisted arene C-H iodination using inorganic iodide as the coupling reagent by employing palladium complexes. By treating simple arene(1 ml) with potassium iodide (0.2 mmol) and PhI(TFA)2 (2.0 equiv) as the oxidant in the presence of [Pd(qin)(OAc)]2 complex (5 mol%) and pyridine (10 mol%), a wide scope of simple non-directing arenes can be halogenated in good yields.