Sulfamic Acid → 4-{[3-Methyl-6-(methyloxy)-2-phenyl-1-naphthalenyl]oxy}benzoic acid

Participants

Reaction Steps

To a round-bottomed flask containing 4-{[3-methyl-6-(methyloxy)-2-phenyl-1-naphthalenyl]oxy}benzaldehyde (8) (0.157 g, 0.426 mmol) was added 6 mL of an acetone:water (2:1) solution. The slightly turbid solution was cooled in an ice-water bath and sulfamic acid (0.097 g, 0.999 mmol, 2.3 eq) was added portionwise over five minutes. The reaction mixture was stirred for 5 min and sodium chlorite (80% tech. Grade) (0.059 g, 0.52 mmol, 1.23 eq) was added portionwise. The reaction mixture was stirred for 40 min. The acetone was removed in vacuo and the crude product was partitioned between water and CH2Cl2. The organic phase was separated, washed with brine, dried over MgSO4, filtered, and the filtrate was concentrated to give 0.155 g of crude 4-{[3-methyl-6-(methyloxy)-2-phenyl-1-naphthalenyl]oxy}benzoic acid as an amorphous solid. Flash chromatography over SiO2 with CH2Cl2:MeOH (96:4) gave the impure 4-{[3-methyl-6-(methyloxy)-2-phenyl-1-naphthalenyl]oxy}benzoic acid. Attempted precipitation of the impurity from a solution of 4-{[3-methyl-6-(methyloxy)-2-phenyl-1-naphthalenyl]oxy}benzoic acid in MeOH had failed to purify the compound. Therefore, the impure 4-{[3-methyl-6-(methyloxy)-2-phenyl-1-naphthalenyl]oxy}benzoic acid (0.105 g) was dissolved in CH2Cl2 (6 mL) and the stirred solution was cooled in an ice-water bath. To the cold solution was slowly added BBr3 (1 M in CH2Cl2) (0.82 mL, 0.82 mmol) and the reaction mixture was stirred under N2 with cooling for 3 h. The reaction mixture was partitioned between CH2Cl2 and water. The organic phase was separated, washed with brine, dried over MgSO4, filtered, and the filtrate was concentrated to give 0.115 g of the crude title compound. The crude title compound was purified by reverse phase preparative HPLC using an CH3CN:H2O gradient (25:75 to 100:0) with 0.05% TFA as a modifier to give 0.013 g (8% from FN1, Step 5) of the title compound (19) as an off-white solid. 1H NMR (400 MHz; DMSO-d6): δ 2.14 (s, 3H), 6.64 (d, J=8.8 Hz, 2H), 6.98 (dd, J=2.2 Hz, 8.9 Hz, 1H), 7.15 (m, 3H), 7.21 (m, 1H), 7.27 (m, 2H), 7.48 (d, J=9.1 Hz, 1H), 7.58 (s, 1H), 7.70 (d, J=8.8 Hz, 2H), 9.86 (s, 1H), 12.58 (br s, 1H). HRMS (ESI) Calcd for C24H17O4: 369.1127 (M−H)−. Found: 369.1148.

Provenance & Evidence