I have not done this yet, but this is how AA said I could use AA.com to book my corporate travel on the web:
1) Call meeting services desk at 800-433-1790 to find out the star-file code for your corporate discount.
2) Create/reserve your itinerary on the web.
3) BEFORE puchasing the ticket, call web technical support at 800-222-2377 and give them the star-file code for your discount. You must state, "I do not want to book this ticket through my corporate travel agent. I want to buy it directly from AA." Some corporate agreements apparently require agency booking unless the client specifically refuses.
Please let us know if this works!