This is possible but you will need to make some minor customization to show a hidden field on the PR pages. You will need to expose the negotiation required flag on the Enter Requisition page and on the Edit and Submit pages. This will allow your requestor to flag the PR as requiring a negotiation (quote). After the approval process it will be available to buyers and category managers in the process requisitions task in the purchasing area. From here a category manager can select the requisition which is flagged as negotiation required and convert it into an RFQ in the Sourcing module. After you create your RFQ you will send it to suppliers for them to respond. After they respond you will need to close the RFQ and make an award decision. This will allow you to complete the RFQ and convert the award decision into a Purchase Order.
HOw to enable negotiation req flag? .can you share your customisation screenshot for reference
I am not sure exactly how to do it in EBS however in the Oracle Fusion Procurement Cloud you need to create a sandbox and make a page customization to the edit and submit requisition pages. In the header section there is a hidden section called negotiation required.