Practical catalytic arylation of C–H bonds by iron/phenanthroline systems

Abstract

In Chapter 1, an overview is given of the current status of the field of non-precious metal catalyzed/mediated direct arylation reactions. Reports on direct arylations catalyzed by Fe, Co, Ni and Cu are mainly demonstrated and discussed. Chapter 2 described a pre-made iron-based catalytic system that is able to catalyze the direct arylation reaction between aryl halides and unactivated arenes under aerobic conditions and using non-distilled benzene as solvent and reagent. Chapter 3 focuses on unraveling structural information of the FPsystem and acquiring an understanding of the evolution of iron species during the direct arylation reactions. By employing a combination of IR, UV-Vis and XAS (XANES and EXAFS) techniques, together with the information from elemental analysis and ICP-OES, a conclusion can be draw that the main component in different FPE systems is almost the same, while in FPM systems (generated in methanol) these are quite different. The constitution of the main component in FP2Eand FP1M was proposed to be [Fe(phen)Cl3(CH3CH2OH)]∙0.5CH3CH2OH ∙0.5phen and [Fe(phen)2Cl2][FeCl4], respectively. Further investigation of FP2Esystems was performed in Chapter 4. First, a kinetic study of the FP2Ecatalyzed direct aryaltion of 4-iodoanisole and benzene in air under reflux was carried out. The comparison of catalytic reactivity of FPE and FPM systems were carried out in this chapter, too. In Chapter 5 the application of FP2E in the Heck-type reaction between 4-iodoanisole and styrene in air was investigated. However, initial results showed that the combination of the applied base and alcohol additive is able to catalyze such transformations in air albeit with moderate yield (58%). Following the observation, the effects of base, alcohol additive, and solvent on the air tolerance of this kind of reaction were investigated in this chapter. The employment of KOtBu and DMF proved to be crucial to the success of the Heck-type reaction in air with non-distilled solvent. A possible mechanism was proposed, which involves radical intermediates formed from the reaction between KOtBu and DMF.