Direct Aromatic Reaction Of Palladium - Catalyzed Simple Electron - Deficient Fluoroaryl

Pd-catalyzed direct C-H arylation with aryl halides, as an efficient route for construction of C-C bond without pre-preparing organometallic reagents, has attracted significant attention in recent years. A series of direct C-H arylations of electron-rich arenes with aryl halides have been reported. However, only few studies focused on electron-deficient arene substrates, because they are less efficient under the electrophilic pallation mechanism. In this thesis, we describe Pd(OAc)2and imino-N-heterocyclic carbene palladium complexes catalyzed direct arylation of electron-deficient fluoroarenes (e.g.1,3-bis(trifluoromethyl)benzene) with aryl bromides with weta-selectivity as follow:In section one:We developed two efficient methods for direct arylation of electron-deficient fluoroarenes. One protocol did not employ an external ligand and the other introduced mono-N-protected amino acid ligands to assist the reaction to proceed under mild conditions. And C-H activation of electron-deficient arenes may experience CMD process under the two optimized conditions. Hence the selectivity is attributed to the variation in the acidity of C-H bonds and the steric hindrance of simple electron-poor arenes.In section two:Imino-N-heterocyclic carbene palladium(II) complex as an efficient catalyst in the arylation of simple electron-deficient arenes with aryl bromides could give good to excellent yields of coupling products with meta-selectivity. The imino nitrogen in imino-N-heterocyclic carbene ligand may play as an internal base to benefit the C-H cleavage in CMD mechism. At the same time, the bulk substituted group in imino nitrogen may protect the coordination vacant in the center metal. It is worth nothing that a relatively low temperature (80℃) is already sufficient to afford moderate to excellent yields with mono-N-protected amino acid assistance.