C-H bond arylation

Consequently, we were faced with the task of formulating a widely acceptable and consistent definition of bond activation . Our research, discussions, and analyses led to a conclusion that bond activation should refer to a process of increasing the reactivity of a bond in question and as such encompasses an entire spectrum of possible mechanisms. Also, we argue that activation is not equivalent to reaction or, in other words, that activation of a bond is not the same as cleavage of a bond. For the latter process we proposed the general term bond transformation . It should be emphasized that both bond activation and bond transformation are general terms and, therefore, information about the reaction and mechanism category should be specified by additional descriptors (cf. C-H bond arylation via electrophilic metalation, C-H bond metalation via concerted metal insertion). 

As an example, Schiff base 1, with its bidentate chelation separated by a three-carbon fragment (the correct distance for formation of a six-membered metalla-cycle) from the C-H bond, can undergo palladium-catalyzed C-H bond arylation... 

Palladium and copper-catalyzed arylation of C-H bonds by aryl halide reagents is reviewed. The emphasis of the review is on directing-group-containing arene and alkane arylation catalyzed by palladium and on sp2 C-H bond arylation catalyzed by copper. Literature up to early 2009 is covered. 

Copper is underutilized as a catalyst for C-H bond functionalization even though it was the first transition metal shown to promote carbon-hydrogen bond arylation. In 1941, Steinkopf, Leitsmann, and Hofmann showed that Ullmann reaction of 2-iodothiophene produces substantial amounts of tritiophene [88], This reaction necessarily involves one C-H bond arylation step. Subsequently, it has been shown that electron-deficient arenes such as polynitrobenzenes and pentafluorobenzene,... 

Abstract This review details recent developments in the Pd-catalyzed C-H bond arylation and alkenylation of indoles and pyrroles, aromatic heterocycles that are frequently displayed in natural products and medicinal agents. 

Regioselective Pd-Catalyzed C-H Bond Arylation on Indole and Pyrrole. 94... 

Scheme 21 Controllable and selective Cu-catalyzed C-H bond arylation of indole...

Abstract A review is presented of synthetic methods for the preparation of biaryls by the rhodium-catalyzed C-H bond arylation of arenes with aryl halides (C-H/ C-X couplings), arylmetal reagents (C-H/C-M couplings) and arenes (C-H/C-H couplings), with an emphasis on postulated mechanisms and their implications on reactivity, selectivity and substrate scope. 

A number of research groups have developed rhodium-catalyzed methods for the C-H bond arylation of arenes that likely proceed through cyclometalated intermediates. Aryl phosphites and phosphinites undergo facile orthometalation... 

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