Hi Brian,
You will likely experience some unexpected behavior since they share the same database, and Service Catalog 14.1 would upgrade the MDB to a version newer than Service Desk uses, so Service Desk will probably have some issues with the common tables. We would strongly recommend against this, even if it is possible to do.
If I may ask, why are you interested in this setup? It is possible that there is a better way to do what you are trying to accomplish.
Regards,
Marty