A rhodium-catalyzed coupling reaction of 2-trimethylsilylphenylboronic acid with internal alkynes is developed for the synthesis of 2,3-disubstituted benzosilole derivatives. A range of functional groups, encompassing ketones, esters, amines, aryl bromides, and heteroarenes, are compatible, which provides rapid access to diverse benzosiloles. Sequential 2-fold coupling enables modular synthesis of asymmetrically substituted 1,5-dihydro-1,5-disila-s-indacene, a π-extended molecule of interest in organic electronics. In terms of the mechanism, the reaction involves cleavage of a C(alkyl)-Si bond in a trialkylsilyl group, which normally requires extremely harsh conditions for activation. Mechanistic studies, including effects of substituents, reveal that C-Si bond cleavage does not proceed through a hypercoordinated silicon species, but rather through a rhodium-mediated activation process. The potential use of the reaction in catalytic asymmetric synthesis of Si-chiral benzosiloles is also demonstrated.
The reaction of 2-(trimethylsilyl)phenylboronic acid with alkynes in the presence of a rhodium catalyst affords benzosilole derivatives. The arylvinylrhodium intermediate undergoes formal substitution at a silicon center, resulting in the cleavage of a robust silicon-methyl bond in the trimethylsilyl group.
The dimerization of styrene derivatives in the presence of a rhodium catalyst proceeds to give stilbene derivatives, in which the ortho C-H bond of styrenes is cleaved and functionalized.
An intramolecular nucleophilic substitution at silicon using organolithium reagents via the cleavage of an inert carbon–silicon bond has been developed as a viable tool for the synthesis of six-membered silacycles.
Six-membered silacycles are available via the cleavage of an inert carbon-silicon bond using organolithium reagents. -(ONOE, M.; MORIOKA, T.; TOBISU*, M.; CHATANI, N.; Chem. Lett. 42 (2013) 3, 238-240, http://dx.
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