Direct arylation overview

The transition metal catalyzed synthesis of arylamines by the reaction of aryl halides or tri-flates with primary or secondary amines has become a valuable synthetic tool for many applications. This process forms monoalkyl or dialkyl anilines, mixed diarylamines or mixed triarylamines, as well as N-arylimines, carbamates, hydrazones, amides, and tosylamides. The mechanism of the process involves several new organometallic reactions. For example, the C-N bond is formed by reductive elimination of amine, and the metal amido complexes that undergo reductive elimination are formed in the catalytic cycle in some cases by N-H activation. Side products are formed by / -hydrogen elimination from amides, examples of which have recently been observed directly. An overview that covers the development of synthetic methods to form arylamines by this palladium-catalyzed chemistry is presented. In addition to the synthetic information, a description of the pertinent mechanistic data on the overall catalytic cycle, on each elementary reaction that comprises the catalytic cycle, and on competing side reactions is presented. The review covers manuscripts that appeared in press before June 1, 2001. This chapter is based on a review covering the literature up to September 1, 1999. However, roughly one-hundred papers on this topic have appeared since that time, requiring an updated review. 

The most common mechanism of C-H bond cleavage in the arylation examples discussed above has been assumed to be electrophilic aromatic substitution involving reaction of an electrophilic palladium catalyst with an electron rich, nucleophilic aromatic ring. In order to effect direct arylation on simple, electron deficient arenes, a basic directing group or intramolecular reaction is usually necessary to enable formation of a metalocycle. As a brief introduction to the effect of this area on the functionalization of indoles and pyrroles, we provide an overview of the mechanistic... 

Although the direct arylation reactions catalyzed by transition metal complexes (other than palladium) are discussed in this chapter, the corresponding palladium-catalyzed transformations are summarized in Chapter 10. A detailed overview of the mechanistic aspects of metaldirect arylations is provided in Chapter 11. 

In Chapter 8, which is complementary to the previous chapter, the direct arylation at the a-position of carbonyl compound substrates (e.g., amides and esters) is discussed. Once again, the catalytic systems and experimenttil conditions are carefully overviewed. 

Transition-metal-catalyzed direct arylation of arenes with aryl halides via cleavage of aryl C—H bonds serves as a straightforward method for aryl-aryl bond formation [3], Hence, direct arylation of two aromatic rings tethered by aromatic/alkenyl moieties or heteroatoms (i.e. intramolecular variant of the direct arylation) constitute efficient syntheses of PAHs such as benzofurans, carbazoles, dibenzothiophenes, dibenzosiloles, and phenanthrenes. In this section we overview the progress with subsections categorized by product structures [5]. 

In Chapter 1, Li and Bo provide an overview of the key chemistry, including Stille coupling, Suzuki coupling and direct C-H arylation, for the synthesis of conjugated polymers used for OPVs. The reaction mechanism and... 

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