Metalation of arenes

The neighboring group-assisted metalation of arenes and heterocycles is an area too vast to be included into this Chapter. Major aspects have been summarized in Chapter 10 of this book and a comprehensive, though still not exhaustive treatment of this theme can be found in a recent monograph. ... 

Another instructive scenario may be found when considering the metalation of arenes. There are two distinct mechanisms for the metalation of aromatic C-H bonds - electrophilic substitution and concerted oxidative addition (Box2). The classical arene mercuration, known for more than a century, serves to illustrate the electrophilic pathway whereas the metal hydride-catalyzed deuterium labeling of arenes document the concerted oxidative addition mechanism [8, 17]. These two processes differ both in kinetic behavior and regioselectivity and thus we may appreciate the need to differentiate these two types of process. However, the choice of C-H bond activation to designate only one, the oxidative addition pathway, creates a similar linguistic paradox. Indeed, it is hard to argue that the C-H bond in the cationic cr-complex is not activated. 

All the above-mentioned metallations of arenes with superbasic reagents are reported in Table 5. 

Electron-deficient rhodium(III) complexes participate in the electrophilic metalation of arenes, as originally shown by Aoyama, Ogoshi, and co-workers [60,61], Highly electrophilic rhodium(III) complexes have also been employed in other reactions that involve the C-H functionalization of arenes, such as the carboxylation of... 

The [(OEP)Rh]+ scaffold, while efficient at the metalation of arenes, is ill-suited for catalytic biaryl bond formation. The generation of an intermediate bearing two aryl groups cis to each other as a typical precursor to biaryls through reductive elimination is impossible due to the ligand-imposed geometry at the metal center. Nonetheless, other highly electron-deficient Rh(III) complexes can offer suitable entries into catalytic routes for electrophilic arene arylation. This is especially the case if the electrophilic Rh(III) center can be accessed in situ from the oxidative addition of Ar-X to a Rh(I) complex (Scheme 4). 

The first observation of metallation of arene in (arene)Cr(CO)3 complex was reported in 1968 [1] and the topic has been included in several reviews [2-10]. 

For regioselective functionalizations of substituted arenes through directed ortho-metaUation reactions with stoichiometric amounts of organometaUic bases, see (a) Snieckus, V. and Macklin, T. (2005) Metallation of arenes. Directed ortho and remote metallation (DoM and DreM), in Handbook of C-H Transformations (ed. 

DIRECTED METALATION OF ARENES WITH ORGANOLITHIUMS, LITHIUM AMIDES, AND SUPERBASES... 

Schlosser introdueed the eoneept of optional site selectivity through mechanism-based substrate reagent matching to describe the metalation of arenes carrying two different DMGs... 

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