flat to drop conversion
 

My beloved commuter is a flat bar road bike. I'm pondering changing it to drops after a long time of thinking about it, and many miles.
My question is this...why won't a set of R-500 "brifters" work with my 440 front derailleur (in the shimano "flat bar road bike line.") I'm currently using a Deore rear derailleur (I know, crossing the streams!) with my current shifters, and it works just fine. Also, not on the shimano compatability charts.

Does anyone know if this will work? And if not, can you explain to me why? I appreciate the help.

If that came across as confusing...it did to me re-reading it. The question is:
R-500 "brifters" + flat bar roadie front derailleur + deore rear derailleur;

Functional? Or will the universe (or my bike) explode upon combining the above?