It’s using (B)oron though, not (Br)omine.

The thing though, is that boron would normally be written before chlorine. So, I would guess what is written is just the reagents and not the final product. Maybe boron trichloride? I haven’t taken a chem class in 15 years, so I may be a bit out of touch though.

Also, what looks to be trichloride (Cl[3]) could also be carbon triiodide, if the person didn’t use serifs for the “I”. Though, both don’t really exist outside of reactions AFIK. The handwriting for subscripted “3” also makes it look like a lowercase “I” making it carbon and lithium. But again, a chemical with just a single carbon and lithium atom doesn’t really exist either.