Here is an inventive technique to do just that, and gain four big points in a sport BJJ match. However, I’m not sure about why you’d want to go for the back in this situation. The way it’s demonstrated in the video, he has the Omoplata locked in, and there is little need to give it up to take the back. I’m confused.
Regardless, you might find this working for you. Absorb this information and see if you find it useful.