How ajax open a link of node in custom region?
I don't have much time to write the example code for you at this moment, please try to digest the steps below. Let me know if you find some points which you don't understand.


Duplicate a new ajax endpoint (e.g. ajax/node/%node) fornode/%nodeinhook_menu`.
Alter the menu item 'node/%node' with custom page callback.  
In the custom page callback, load front page content.
Load a custom JS file in the page callback.
In block admin, move a empty block to the desire region.
In the custom JS file, use l_ajax() to load the content ajax/node/%node to the target DIV.