Oxidation with e.g. HgO: Org. Synth. Coll., 3, 351 (1955), peracetic acid and tetramethylguanidine: J. Chem. Soc., Perkin 1, 2030 (1975), iodosobenzene diacetate: Synthesis, 513 (1985) or potassium monopersulfate: Tetrahedron Lett., 38, 1239 (1997), gives diphenyldiazomethane, a reagent for the protection of carboxylic acids by conversion to their benzhydryl esters. The protecting group can be cleaved by hydrogenolysis: Helv. Chim. Acta, 31, 439 (1938), or mild acid: J. Am. Chem. Soc., 87, 3969, 5469 (1965).
