Silylation of arenes

The iridium complex composed of l/2[ Ir(OMe)(cod)2 ] and 4,4 -di-/ r/-butyl-2,2 -bipyridine (dtbpy) shows a high catalytic activity for aromatic G-H silylation of arenes by l,2-di-/z r/-butyl-l,l,2,2,-tetrafluorodisilane.142 The reaction of 1,2-dimethylbenzene with l,2-di-/< r/-butyl-l,l,2,2,-tetrafluorodisilane in the presence of l/2[ Ir(OMe)(cod)2 ] and dtbpy gives 4-silyl-l,2-dimethylbenzene in 99% yield (Equation (103)), which can be utilized for other functionalizations such as arylation and alkylation. 

The direct silylation of arenes through C—H bond activation provides an attractive route for the synthesis of useful aromatic compounds [64]. Vaska s complex was the first of the iridium catalysts to be reported for activation of the C—H bond in benzene by Si—H of pentamethyldisiloxane to yield phenylsubstituted siloxane [65]. However, a very attractive method for the aromatic C—H silylation with disilanes has been recently reported by the groups of Ishiyama and Miyaura [66-68]. 

Silylation of arenes was reported to take place with rhodium and iridium complexes as the catalyst. The Vaska complex effects the reaction of benzene with pen-tamethyldisiloxane,230 whereas [RhCl(CO)(PMe3)2] catalyzes the formation of C—Si bonds under irradiation231 [Eq. (10.39)] 232... 

Transition-metal Catalyzed Silylation of Arenes 131 Fumitoshi Kakiuchi... 

A very attractive method for the dehydrogenative silylation of arenes via the C-H bond cleavage has been recently reported by Kakiuchi et al. [15]. The reaction of aryloxazolines with trialkylsilanes (mostly triethylsilane) catalyzed by Ru complexes results in the formation of ortho-silylated aryloxazolines in good-to-excellent yields (Eq. 7). 

A similar silylation reaction of benzene with triethylsilane also took place under photoirradiation conditions [88]. Lower catalyst loading improves the selectivity of the corresponding silylbenzene (Eq. 43). This catalyst system can also be applied to the dehydrogenative silylation of arene with hexaorganodis-ilane. 

The borylation and silylation of arenes and alkanes with borane and silane reagents are exceptions. 

Cheng, C. Hartwig, J. F. Rhodium-catalyzed intermoleeular C—H silylation of arenes with high steric regiocontrol. Science. 2014, 343, 853-857. 

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