METHYL 3-HYDROXY-2-NAPHTHOATE

General Description

Methyl 3-hydroxy-2-naphthoate undergoes asymmetric oxidative coupling using mono-N-alkylated octahydrobinaphthyl-2,2′-diamine chiral ligands.

Synthesis

Methyl 3-hydroxy-2-naphthoate is obtained by reacting 3-hydroxy-2-naphthoic acid with methanol in sulphuric acid.3-hydroxy-2-naphthoic acid (1.00 g, 5.31 mmol) was dissolved in methanol (20 ml) and concentrated sulphuric acid (1 ml) and left to reflux overnight with stirring. The reaction mixture was washed with brine (2×10 ml) and extracted with ethyl acetate (3 × 10 ml) upon cooling. The organic extracts were collected, dried with magnesium sulphate and concentrated in vacuo to give the title compound as a yellow powder (976 mg, 91%): mp: 81℃(Lit.: 75 – 76℃);
vmax/cm-1 3178 br. m (O-H), 2952 w (aro. C-H), 1515 m (aro. C=C); δH (300 MHz; CDCl3) 10.47 (1H, s, OH), 8.47 (1H, s, C(1)H), 7.79 (1H, d, J 8.3, C(5)H or C(8)H), 7.68 (1H, d, J 8.3, C(5)H or C(8)H), 7.50 (1H, td, J 7.5, 1.1, C(6)H or C(7)H), 7.36-7.29 (2H, m, C(4)H and C(6)H or C(7)H), 4.02 (3H, s, OCH3); δC (75 MHz; CDCl3) 170.3 (Ar- C), 156.3 (Ar-C), 137.9 (Ar-C), 132.5 (Ar-CH), 129.2 (Ar-CH), 129.1 (Ar-CH), 127.1 (Ar-C), 126.3 (Ar-CH), 124.0 (Ar-CH), 114.2 (Ar-C), 111.7 (Ar-CH), 52.6 (OCH3); m/z (-ES) 201 (100%, [M-H]-), 202 (14%, [M]-).

Purification Methods

Crystallise the ester from MeOH (charcoal) containing a little water. [Beilstein 10 IV 1186.]