Ring-closing carbonyl-olefin metathesis (COM) reactions provide a straightforward method for producing cyclic alkenes from precursors containing carbonyl functional groups tethered to nucleophilic alkenes. Within the last decade, many methods for carrying out Lewis acid- or organocatalyzed COM reactions were reported; however, Brønsted–Lowry acid-catalyzed COM reactions are less developed. Herein, we report that phosphoric acid derivatives and N-triflylphosphoramides mediate COM reactions, although the substrate scope is limited to biaryl compounds that cyclize to produce phenanthrene products. We also disclose the synthesis and characterization of a previously non-fully characterized phosphoric acid derivative and a novel phosphoramide.