[mps]

I could use some help with the mechanism at work here:

How can acetoacetic ester (AAE) be used with alkyl halide (eg CH3Cl) to form ketone (eg 2-butanone)?  I can't see how we're cleaving the bond between an alpha-C and carbonyl-C. 

Brainstorming 2 mechanisms:
The first step may be Nu attack on carbonyl-C.  Our solvent is (sodium) ethoxide, so we have a good Nu.  This pushes pi e- from carbonyl C=O bond onto carbonyl O, and carbonyl-C is now sp3 hybridized.  But, if this were the mechanism, still not clear how C-C bond is broken.

Other mechanism may be enolization of carbonyl O.  A carbanion intermediate immediately precedes the formation of C=C pi bond, which itself can act as Nu in SN2 (presumably AAE is far too bulky for SN1), displacing halide from alkyl halide, and adding R.  Now we have a tertiary C between the two carbonyl carbons.  Again, how can we cleave this bond??

Million thanks.  If there's a general principle or concept I've overlooked, it would be great if you'd point that out.  Thanks again.

Patrick     

[movies]

Typically you would do this in two steps.  The first step is a simple alkylation on the carbon between the two carbonyls.  In the second step you would saponify the ester to the carboxylate, which would then decompose by liberation of carbon dioxide to an enolate.  Protonation of the enolate would give the desired ketone.

[mps]

Thanks, movies.  But how's the first alkylation achieved-- through Nu susbtitution using enolate carbanion?  Is this typical SN2?

[movies]

It depends on the electrophile.  With something like MeI, it would be an S_N2 mechanism.  With something like ethyl acrylate, it's a conjugate addition mechanism, which is a little different.

[alphahydroxy]

Can you draw up a scheme please ?

[movies]

I assume you know what a S_N2 mechaism looks like.  The conjugate addition can be found here.

[alphahydroxy]

I was asking the OP to put up the reaction scheme...

[m3lm4k]

I hope I have not made any mistake