Water → 2,3-Dihydroxy-4-methylbenzaldehyde

14 (770 mg, 4.6 mmol) was placed in solution in DCM (8 mL) under nitrogen and the solution was cooled down at −20° C. while stirring. Boron trichloride 1M in DCM (10 mL, 9.2 mmol) was added slowly over 15 minutes keeping the temperature below −20° C. The reaction mixture turned from yellow to dark red and was left stirring and warming up overnight. More boron trichloride (5 mL) was added in the morning at T<−20° C. and the reaction was left stirring overnight after which the reaction appeared complete by LC-MS. The mixture was poured into water and extracted with ethyl acetate. The organic phase was dried over sodium sulphate, filtered and evaporated. The crude product was columned on silica with neat DCM to yield 306 mg of 15: