Triphenylphosphine → 3-Chloro-4-(propan-2-yloxy)benzoic acid

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Propan-2-ol (2.45 ml) and PPh3 (1.18 g) were dissolved in THF (30 ml), cooled to 0° C., treated with methyl 3-chloro-4-hydroxybenzoate (6.00 g) followed by the drop-wise addition of DIAD (9.44 ml) and stirred at RT overnight. The reaction mixture was then evaporated and purified on silica cartridges (4×100 g), eluting with a 0 to 40% mixture of EtOAc in pentane to give the crude product (7.00 g) as a colourless oil. This was dissolved in MeOH (30 ml) and 2 M aqueous NaOH (30 ml) and stirred at RT for a weekend. The reaction mixture was then evaporated and re-dissolved in H2O. This solution was washed with Et2O, acidified to pH=1 and extracted with Et2O. These latter extracts were dried over MgSO4, filtered and evaporated to give the title compound (4.16 g) as a white solid. δH (MeOD, 400 MHz): 1.37 (6H, d), 4.77 (1H, septet), 7.12 (1H, d), 7.90 (1H, d), 7.98 (1H, s). MS (ES): C10H11ClO3 requires 214; found 215 (MH+).

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