[noda]

How did the Desilylation with TBAF accomplished (in terms of mechanism) in the next scheme?
The solvent of the Desilylation is THF.

[movies]

What do you think?

[noda]

fluoride attack the silyl and then depart the product, but I'm not so sure about that because fluoride is lousy Nu , I think it's occur because of the strong bond of silyl fluoride, but why are we need big alkyl groups, is it due to the Organic solvent(THF)?
what is the role of the big alkyl groups? I think it involves phase transfer catalyst, but I'm not so sure.

[movies]

Yeah, you have the right idea.  F- is usually a poor nucleophile, but that's often because it gets bound up with something like H+.  In this case, the counter ion is a really big, diffuse, non-coordinating thing, so the F- is pretty available as a nucleophile.  Also, the Si-F bond that you make is really strong, so there is a big downhill driving force for the reaction to occur.