First Brønsted Acid-Induced Ring Expansion of an Oxaphosphirane Complex: A Combined Experimental and DFT Study

First examples of Brønsted acid-induced P,O bond-selective ring expansion reactions of a transition metal coordinated σ3λ3-oxaphosphirane derivative are described. The method provides new and high-yield access to 4,5-dihydro-1,3,4-oxazaphosphole complexes 5a,b−7a,b using oxaphosphirane complex 1 and trifluoromethanesulfonic acid in the presence of different carbonitriles, followed by treatment with triethylamine. A DFT-based reaction course is proposed.