Abstract
Direct activation of carbon–fluorine bonds (C–F) to introduce the silyl or boryl groups and generate valuable carbon–silicon (C–Si) or carbon–boron (C–B) bonds is important in the development of synthetically useful reactions, owing to the unique opportunities for further derivatization to achieve more complex molecules. Despite considerable progress of C–F bond activation to construct carbon–carbon (C–C) and carbon–heteroatom (C–X) bond formation, the defluorosilylation via C–F cleavage has been rarely demonstrated. Here, we report an ipso-silylation of aryl fluorides via cleavage of unactivated C–F bonds by a Ni catalyst under mild conditions and without the addition of any external ligand. Alkyl fluorides are also directly converted into the corresponding alkyl silanes under similar conditions, even in the absence of the Ni catalyst. Applications of this protocol in late-stage defluorosilylation of potentially bioactive pharmaceuticals and in further derivatizations are also carried out.
Highlights
Direct activation of carbon–fluorine bonds (C–F) to introduce the silyl or boryl groups and generate valuable carbon–silicon (C–Si) or carbon–boron (C–B) bonds is important in the development of synthetically useful reactions, owing to the unique opportunities for further derivatization to achieve more complex molecules
One of the recent significant achievements in this area is the defluoroborylation independently reported by the groups of Martin and Hosoya; this method still is limited since it inevitably requires the use of electron-rich and expensive ligands such as phosphines or N-heterocyclic carbenes (NHCs), as well as relatively high temperatures (Fig. 1b, path b)[14,15]
Prompted by the versatility and pivotal role of organosilicon compounds[16], as well as by our ongoing interest in the activation of inert C–F bonds[17], we report an available example of the ipso-silylation of aryl and alkyl fluorides via cleavage of unactivated C–F bonds under catalytic conditions mediated by Ni or in the absence of metal catalyst (Fig. 1c)
Summary
Direct activation of carbon–fluorine bonds (C–F) to introduce the silyl or boryl groups and generate valuable carbon–silicon (C–Si) or carbon–boron (C–B) bonds is important in the development of synthetically useful reactions, owing to the unique opportunities for further derivatization to achieve more complex molecules. Prompted by the versatility and pivotal role of organosilicon compounds[16], as well as by our ongoing interest in the activation of inert C–F bonds[17], we report an available example of the ipso-silylation of aryl and alkyl fluorides via cleavage of unactivated C–F bonds under catalytic conditions mediated by Ni or in the absence of metal catalyst (Fig. 1c). By means of this process, we have prepared a broad variety of aryl silanes and alkyl silanes. The present method is an extremely rare example of a defluorosilylation reaction using silylated reagents
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