Supersilylating agent

While the reduction in eq 4 is not stereoselective, the stereo-controlled elaboration of (14) may be achieved in principle via conformationally biased carbocations (15). This has been demonstrated for the allylation of (14) with allyltrimethylsilane (eq 5). The major products (16) appear to derive from axial attack on (15). The most effective catalyst was TfOH2+B(OTf)4, which could be used at levels of 1-2 mol % and gave yields of 78-85% with dr > 20 1. While it is possible that the superacid acts by protonation of the alkoxy oxygen in (14), it is probably more likely that the active species is the supersilylating agent MesSi B(OTf)4, derived from superacid and allylsilane. 

Preparation of Supersilylating Agents. TIPSCl reacts with boron tris(trifluoromethanesulfonate) or B(OTf)3 in CH2CI2 to form a so-called supersilylating agent with 1 1 stoichiometry (eq 18). ... 

One of the many applications of the supersilyl sodium just introduced concerns its use as an excellent dehalogenation agent. It transforms, for example, the dibromodisilane R Br2Si-SiBr2R in THF quantitatively into tetrasupersilyl-tetra/iedetailed studies on the mechanism of the dehalogenation reactions,... 

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