Triphenylphosphine → Methyl 3-bromo-5-formyl-4-methylbenzoate

To a dichloromethane (0.16 M) solution of methyl 3-bromo-5-[(1E)-3-methoxy-1-propen-1-yl]-4-methylbenzoate (1 eq., Amine 88, Step 1) was bubbled at −78° C. with freshly generated ozone until a persistent blue color was observed. The reaction vessel was then thoroughly purged with nitrogen before triphenylphosphine (1.1 eq.) was added. The resulting mixture was slowly warmed to RT over 6 h. The volatiles were then removed in vacuo and the resulting residue was suspended in a 1:1 (v/v) mixture of hexanes and ether. The insolubles were removed via filtration through a pad of silica gel. Concentration of the filtrate thus obtained in vacuo afforded a white solid. Further purification of the crude product by way of flash chromatography (SiO2, Hex→1:1 (v/v) Hex:EtOAc) afforded the title compound as a white solid.