Metal groups arylation

Reactivity and yields are greatly enhanced by the presence of 0.5-1% Na in the Li. The reaction is also generally available for the preparation of metal alkyls of the heavier Group 1 metals. Lithium aryls are best prepared by metal-halogen exchange using LiBu" and an aryl iodide, and transmetalation is the most convenient route to vinyl, allyl and other unsaturated derivatives ... 

Derivatives of the boranes include not only simple substituted compounds in which H has been replaced by halogen, OH, alkyl or aryl groups, etc., but also the much more diverse and numerous class of compounds in which one or more B atom in the cluster is replaced by another main-group element such as C, P or S, or by a wide range of metal atoms or coordinated metal groups. These will be considered in later sections. 

In hydrogenation, early transition-metal catalysts are mainly based on metallocene complexes, and particularly the Group IV metallocenes. Nonetheless, Group III, lanthanide and even actinide complexes as well as later metals (Groups V-VII) have also been used. The active species can be stabilized by other bulky ligands such as those derived from 2,6-disubstituted phenols (aryl-oxy) or silica (siloxy) (vide infra). Moreover, the catalytic activity of these systems is not limited to the hydrogenation of alkenes, but can be used for the hydrogenation of aromatics, alkynes and imines. These systems have also been developed very successfully into their enantioselective versions. 

FIGURE 1. Nomenclature for O atoms in constitutionally asymmetric peroxides (R = alkyl, aryl R = H, metal, transition metal, group 13-17 elements)... 

The M2N2 rings in 10.31 and 10.32 are both planar with the groups attached to the group 14 metal centres (aryl and Cl, respectively) in a trans arrangement... 

Kato, S. Nonoyama, N. Tomimoto, K. Mase, T. Non-cryogenic metalation of aryl bromides bearing proton donating groups formation of a stable magnesio-intermediate. Tetrahedron Lett. 2002, 43, 7315-7317. 

Regioselective substitution reactions of a series of 2- and 3-hydroxybiaryls including BINOL have been performed via a new directed orf/io-metallation procedure.75 O-Aryl AMsopropylcarbamates, conveniently prepared from phenols and isopropyl isocyanate, have been temporarily and in situ N-protected by means of silyl inflates to form stable intermediates for low-temperature lithiation reactions using n-BuLi-TMEDA in diethyl ether. The IV,IV-dialkyl aryl O-sulfamate has been reported as a new directed metallation group.76... 

Group 4-8 transition metal alkyl,aryl or hydride (3)... 

In most of these ligands the chiral center is far removed from the site where the prochiral substrate coordinates to the transition metal, so that little diastereo-differentiation might be expected. However, the chirality of the backbone controls the conformation of the bulky diarylphosphine groups and hence generates a chiral pocket around the metal, with aryl groups in axial and equatorial positions. This imposes C2 symmetry on the complex, as shown in (22-X). Viewed from the side, such a complex can schematically be divided into sterically hindered and open quadrants (22-XI). A prochiral substrate will then naturally bind with the jr-face that leads to the product with the least steric repulsion. 

Metallinos, C., Nerdinger, S., Snieckus, V. N-Cumyl Benzamide, Sulfonamide, and Aryl O-Carbamate Directed Metalation Groups. Mild Hydrolytic Lability for Facile Manipulation of Directed Ortho Metalation Derived Aromatics. Org. Lett. 1999, 1, 1183-1186. 

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