Corriu group

The same hypercoordinate silylene (79) was generated by the Corriu group in dehalogenation reactions the best results were with the difluoride Ar2SiF2 (Ar = o-Me2NCH2Ph) and lithium metal or lithium naphthalene97. The silylene was trapped by 1,4-addition to 2,3-dimethylbutadiene. Similar defluorination reactions were used to obtain silylenes 87-89 shown in Scheme 25, all trapped with dimethylbutadiene. 

A report by the Corriu group, however, shows that this is not necessarily the case (equation 49) . When difluorosilane was treated with lithium metal in the presence of dimethylbutadiene, the silacyclopentene was obtained in good yield but no silylene was intercepted if EtsSiH was present as the trapping agent. The product silacyclopentene could result either from reaction of the diene with a silylenoid, or from reaction of the diene with lithium and trapping of the lithium compound by the difluorosilane. In earlier studies of the alkali metal induced reactions of dihalosilanes with 1,3-dienes, it was found that the diene, rather than the dihalosilane, reacts initially with the metal. ... 

The reaction of aryl electrophiles with organomagnesium compounds is known as Kumada or Kumada-Tamao-Corriu reaction. The most common leaving groups in the electrophile are halogen atoms and, among them, chlorine is the most wanted due to the good availability and the low price of aryl or heteroaryl chlorides. Unfortunately, the oxidative addition of a metal center to an aryl chloride is a difficult reaction and many efforts have been made to overcome existing limitations. 

The stereochemical data reported in the case of germanium compounds by Eaborn et al. 90), Brook and Peddle 91), or Carre and Corriu (92) are quite parallel to those discussed here. The nature of the leaving group and the electronic character of the nucleophile, rationalized in terms of hard and soft reagents, are also the dominant factors that govern the stereochemistry. 

Corriu and coworkers have found that the barrier to pseudorotation seems to depend on the number of electronegative groups present35. For species with one electronegative substituent, AG >20 kcalmol-1. With two electronegative groups, the barrier decreases to ca 9-12 kcalmol-1, and when three electronegative substituents are present, the pseudorotation barrier has A<7 kcalmol-1. 

Corriu and coworkers suggest that Chojnowski s mechanism may only operate with very labile Si—Br and Si—I bonds and good nucleophiles62. They also criticize the mechanism as it cannot account for the nucleophile-induced epimerization of chlorocyclobutanes. As mentioned earlier, in small rings with exocyclic leaving groups, retentive substitution predominates, so that two consecutive substitutions by FIMPA would only lead to retention. 

In 1989, Corriu and workers reported the thermal decomposition (85 °C) of the silyl formate 6, having a remote stabilizing amino group, which was prepared by the insertion reaction of the corresponding pentacoordinated functional silane 5 with CO2,... 

A further contribution to this controversy has recently been added by Corriu s group, showing that, depending on the counter anion and solvent, each of the penta and tetracoordinate structures (162) can predominate, and in one particular case (162d) both were shown to coexist in nearly equal concentrations18613. 

Formal octacoordination ( 4 + 4 )229 in a silicon complex was recently demonstrated by Corriu s group, who prepared 201 (equation 53). The Si-N distances (Table 27) are long relative to those common in penta- and hexacoordinate compounds, but are in the same range as those found in the heptacoordinate compounds discussed here. Also, the geometry resembles the heptacoordinate complexes, in that it is basically a tetrahedron with dimethylamino donor groups pointing toward the center, in what may be termed a tetracapped tetrahedron . 

A single hexacoordinated silatrane 46 possessing a very weak additional Si NMe2 bond (2.952 A) was obtained recently by Corriu and coworkers44. The hexacoordination in 46 is most likely due to the rigid geometry of its 8-dimethylaminonaphthyl group. The reluctance of silicon to become hexacoordinated in the silatrane structure is its special characteristic feature which, as will be shown below (Section II.C), predetermines the low reactivity of silafunctional silatranes toward nucleophiles. 

In 1971, a year before the groups of Corriu and Kumada [5] independently reported the groundbreaking work on the topic of nickel-catalyzed cross-coupling reactions of aryl and vinyl halides with Grignard reagents, Tamura and Kochi described an iron-catalyzed vinylation reaction of Grignard reagents with vinyl halides (Scheme 5.1) [6]. 

Since the discovery of transistion metal-catalyzed cross-coupling reactions by the groups of Kochi, Kumada and Corriu in the early 1970s, impressive progress has been achieved in the development of these methods into a synthetically indispensable... 

The particular versatility of an integrated iodopropyl group was recently demonstrated by Corriu and coworkers.189 In comparison with the chloropropyl group, they could show that the iodo group allows much easier and faster postsynthetic chemical... 

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