It is unlikely that you will get a good match by doing this as the rolloff point will be raised and rolloff slope will become more shallow (12db/oct for sealed vs. 24db/oct for ported).
If possible (even if only while you are listening) it would be better to pull the speakers furrther out from the wall behind. It may even be better to bring the speakers closer together, probably with less toe-in, so that you get the right speaker away from the corner a bit more. If the speakers were say 6' apart, you might want to sit closer to them (6' to 8') than you are now. This more nearfield setup will help to reduce the room effects.
The other alternative is to plug both speakers' ports and add a sub.