Diethyl Ether → Methyl 3-chloro-5-hydroxybenzoate

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The general process was applied to methyl 3-chlorobenzoate (171 mg, 1.0 mmol). The borylation step was carried out neat with HBPin (200 mg, 1.55 mmol) and dmpe (3.0 mg, 0.02 mmol, 2 mol %) at 150° C. for 3 hours. The oxidation step was then performed as described above, after which the crude material was dissolved in ether and passed through a plug of silica gel (pentane/ether 2:1). Evaporation of solvent gave 134 mg phenol 5 (72%) with trace water. Sublimation at 85° C. under 0.06 mm Hg afforded analytically pure 5 as a white solid; mp 133-135° C. (lit. 138-139). 1H NMR (300 MHz, acetone-d6): δ 9.2 (brs, 1 H), 7.43 (t, J=1.7 Hz, 1 H), 7.40 (dd, J=2.2, 1.7 Hz, 1 H), 7.10 (t, J=2.2 Hz, 1 H), 3.87 (s, 3 H); 13C NMR (75 MHz, acetone-d6): δ 165.9, 159.3, 135.3, 133.8, 121.0, 120.6, 115.7, 52.7; IR (neat): 3335, 1690, 1591, 1431, 1350, 1242, 768 cm−1; LRMS: m/e 186 (M+), 155, 127, 99. Anal. Calcd for C8H7ClO3: C, 51.50; H, 3.78. Found C, 51.78; H, 3.73. For a previous preparation see Takahashi et al., Heterocycles 23: 1483-1491 (1985) (three steps from 3,5-dichlorobenzoic acid, 65% overall yield).

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