[sally]

At the mechanism of luche reduction Metoxide attack the sodium, how does it invert to metoxide if the methanol is the solvent
link mechanism of luche reduction: http://www.organic-chemistry.org/namedreactions/luche-reduction.shtm

[Dan]

I'm not entirely sure what you are asking. Do you mean how do you get methoxide ions from the methanol?
If so, it is activation of the methanol with CeCl₃

MeOH + Ce³⁺<-----> MeO-Ce²⁺ + H⁺

MeO-Ce²⁺ being your methoxide ion source. The H⁺ protonates the carbonyl.

[movies]

I don't buy that mechanism.  It's known that NaBH₄ can be used to reduce lanthanides to the corresponding metal hydrides so I think that you make a cerium hydride first and that then reduces the ketone via a 4-membered ring transition state, therefore giving the observed 1,2-reduction.  More evidence for this is that enones are reduced faster than ketones under Luche conditions, presumably because they are more electron rich and thereby coordinate to cerium more rapidly.  If the mechanism shown on that page is right, then you wouldn't expect much of a difference between ketones and enones.

[sally]

can you please draw the mechanism to me or give me a link of the right mechanism?
thank you

[movies]

Well, this is the way that I learned it and I've seen it in several books.  I just looked back at some of the old Luche papers and they seem to favor the mechanism that you drew, although they didn't directly address the possibility of a cerium hydride intermediate.

They most striking piece of evidence I found against this mechanism is that they prepared Ce(BH₄)₃ and CeCl(BH₄)₂ and found that they didn't perform the regioselective reduction reaction effectively.  That's far from a definitive result, but I would expect those complexes to be competent (at least somewhat) in the mechanism below as well.