[raykel]

I know what does but I don't know why it favor Syn over antiSyn let say at low temp -80 C. 

Any help would be appreciated
 

[Dan]

In what reaction?

[raykel]

This is the RXN!!!!

I know that oxygen interact with boron for the first step and then deportation of the alpha carbon (let say with a base). Then its in Z-Enolate, then addition of aldehyde. I know that it is kinetically controlled reaction.

I Want to understand how does the Geometry selection work? 

[Dan]

Start by looking up the Zimmerman-Traxler model

[orgopete]

I haven't looked at this area in quite a while, but I doubt you will find anything definitive. You should be able to find conditions that favor E vs Z-enolates and theories as to why in an advanced organic text. However, if I recall correctly, this is not definitive. Depending on the molecule, you may get the opposite result as well. You should find some ideas and you can use them to predict how a specific example may proceed.

[raykel]

Thanks orgopete

I have bunch of Adv. O CHEM text but will see.

The reason I am asking is because I know my professor will come up with Kinetic Vs thermodynamic product and which structure is energetically favor Z or E enolate, and some steric effect. but I am not convince of these arguments. I want to look at this problem from MO prospective. I want to see if some people have looked at the molecular orbital interaction for reaction like this one.

I have looked at the paper titled "Stereoselective aldol condensations via Boron Enolates" JACS 101:20 Sep 26,1979 as you may guess its steric effect.

Thanks Again
 
I will keep looking and get back for more help