Research Article

Rhodium-Catalyzed Intermolecular C–H Silylation of Arenes with High Steric Regiocontrol

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Science  21 Feb 2014:
Vol. 343, Issue 6173, pp. 853-857
DOI: 10.1126/science.1248042

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Silicon Siting

The synthesis of many pharmaceutical and agrochemical compounds requires selective functionalization of multiple different sites on aromatic ring frameworks. The size and electronic properties of the first substituent added can influence where the next one is likely to end up. Cheng and Hartwig (p. 853, see the Perspective by Tobisu and Chatani) discovered a rhodium-catalyzed reaction that is particularly sensitive to size that places a silicon substituent as far away as possible from the largest group already on the ring. The silicon group can then be replaced with carbon, oxygen, nitrogen, or halide substituents as needed.

Abstract

Regioselective C–H functionalization of arenes has widespread applications in synthetic chemistry. The regioselectivity of these reactions is often controlled by directing groups or steric hindrance ortho to a potential reaction site. Here, we report a catalytic intermolecular C–H silylation of unactivated arenes that manifests very high regioselectivity through steric effects of substituents meta to a potential site of reactivity. The silyl moiety can be further functionalized under mild conditions but is also inert toward many common organic transformations, rendering the silylarene products useful building blocks. The remote steric effect that we observe results from the steric properties of both the rhodium catalyst and the silane.

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