1 research outputs found
Catalytic Reductive <i>ortho</i>-C–H Silylation of Phenols with Traceless, Versatile Acetal Directing Groups and Synthetic Applications of Dioxasilines
A new,
highly selective, bond functionalization strategy, achieved
via relay of two transition metal catalysts and the 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
relay of Ir-catalyzed hydrosilylation of inexpensive and readily available
phenyl acetates, exploiting disubstituted silyl synthons to afford
silyl acetals and Rh-catalyzed <i>ortho</i>-C–H silylation
to provide dioxasilines. A subsequent nucleophilic addition to silicon
removes 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 <i>ortho-</i>C–H silylation of phenols
was also successfully applied to preparation of multisubstituted arenes.
Remarkably, a new formal α-chloroacetyl directing group has
been developed that allows catalytic reductive C–H silylation
of sterically hindered phenols. In particular, this new method permits
access to highly versatile and nicely differentiated 1,2,3-trisubstituted
arenes that are difficult to access by other catalytic routes. In
addition, the resulting dioxasilines can serve as chromatographically
stable halosilane equivalents, which allow not only removal of acetal
directing groups but also introduce useful functional groups leading
to silicon-bridged biaryls. We demonstrated that this catalytic C–H
bond silylation strategy has powerful synthetic potential by creating
direct applications of dioxasilines to other important transformations,
examples of which include aryne chemistry, Au-catalyzed direct arylation,
sequential orthogonal cross-couplings, and late-stage silylation of
phenolic bioactive molecules and BINOL scaffolds