2,3-Dichloro-5,6-dicyano-1,4-benzoquinone → 3-(4-Methyl-benzooxazol-2-yl)-benzoic acid methyl ester

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Reaction Steps

2-Amino-3-methyl-phenol (6.09 mmol) is heated with 3-formyl-benzoic acid methyl ester (6.09 mmol) in MeOH (6 mL) at 60° C. for 30 minutes. The solvent is removed from the mixture to obtain a dark red oil which is dissolved in dry CH2Cl2 (6 mL) at room temperature and treated with DDQ (6.4 mmol) for 16 hours. The mixture is diluted with EtOAc and poured onto saturated aqueous NaHCO3. The aqueous phase is further extracted with EtOAc and the combined organic phases are dried over Na2SO4. Filtration and removal of the solvent yields a residue which is purified by silica gel chromatography (5-10% EtOAc/hexane) to yield 3-(4-methyl-benzooxazol-2-yl)-benzoic acid methyl ester as a white solid: 1H NMR (400 MHz, CDCl3) 8.92 (d, J=1.6 Hz, 1H), 8.47 (dt, J1=7.8 Hz, J2=1.5 Hz, 1H), 8.2 (dt, J1=7.8 Hz, J2=1.4 Hz, 1H), 7.61 (t, J=7.9 Hz, 1H), 7.43 (d, J=8.1 Hz, 1H), 7.27 (t, J=7.7 Hz, 1H), 7.17 (t, J=7.5 Hz, 1H), 3.99 (s, 3H), 2.69 (s, 3H); LC/MS (ES+): (M+1) 268.1.

Provenance & Evidence