A new, highly selective, bond functionalization strategy, achieved via relay of two transition metal catalysts and use of traceless acetal directing groups, has been employed to provide facile formation of C–Si bonds, and concomitant functionalization of a silicon group, in a single vessel. Specifically, this approach involves the Ir-catalyzed hydrosilylation of inexpensive and readily available phenyl acetates, exploiting disubstituted silyl synthons, to afford silyl acetals and Rh-catalyzed ortho-C–H silylation to provide dioxasilines. A subsequent nucleophilic addition to silicon efficiently re-moves the acetal directing groups and directly provides unmasked phenol products and, thus, useful functional groups at silicon achieved in a single vessel. This traceless acetal directing group strategy for catalytic ortho-C–H silylation of phenols was also successfully applied to preparation of multi-substituted arenes. Remarkably, a new, formal α-chloroacetyl directing group has been developed which allows catalytic reductive C–H silylation of sterically hindered phenols. In particular, this new method permits to access to highly versatile and nicely differentiated 1,2,3-trisubstiuted arenes that are difficult to access by other catalytic routes. We demonstrated multiple synthetic potential of this strategy, such as aryne chemistry, Au-catalyzed direct and sequential orthogonal cross-couplings, late-stage silylation of phenolic bioactive molecules, and BINOL scaffolds.

Catalytic reductive ortho-C–H silylation of phenols with traceless, versatile acetal directing groups

254th National Meeting (2017)

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