There is an exit that is called (EXIT_SAPLMEWQ_001) when a requisition is created via the BAPI "BAPI_REQUISITION_CREATE". You can always raise the event yourself from there or just create the e-mail directly from the exit. You should check to see whether the exit gets called from the transaction and not just the BAPI.
Dig Deeper on SAP workflow development
Related Q&A from Alon Raskin
Find out how to configure clients so that the same version of an SAP workflow item is used when the workflow is triggered in separate clients. Continue Reading
An SAP user has created a user decision step in an SAP workflow item and wants to know how an end user can send an attachment to other users. Continue Reading
A SearchSAP.com reader wants to know how to hide the forward button in an SAP Business Workplace toolbar. Continue Reading