Reaction Steps
(E)-3-(5-chloro-2-tetrazol-1-yl-phenyl)-acrylic acid: To a cooled (0° C.) suspension of NaH (0.262 g, 6.56 mmol) in THF (27.3 mL) was added dropwise methyl 2-(dimethoxyphosphoryl)-acetate (1.150 mL, 7.10 mmol). The resulting thick, white suspension was diluted with additional THF (15 mL) to facilitate mixing, then allowed to warm to rt and stirred at rt for 45 min. Next, a slightly cloudy blue solution of 5-chloro-2-tetrazol-1-yl-benzaldehyde (1.14 g, 5.46 mmol), prepared according to a modification of the procedure described by Howard (J. Med. Chem., 2006, 49, 1346.), in THF (8 mL) was added. The yellow/green suspension was stirred vigorously. After 30 min, the reaction was poured into cold sat. ammonium chloride and extracted with EtOAc. The combined organic layers were washed with brine, dried over Na2SO4, filtered and concentrated to give a green/blue solid weighing 1.76 g. The solid was dissolved in EtOAc and filtered through a plug of silica gel, eluting with EtOAc. The green filtrate was concentrated to give a greenish solid weighing 1.36 g. Recrystallization from EtOAc gave an off-white solid weighing 0.476 g. Additional product was obtained by concentrating the filtrate from recrystallization, adding methanol, sonicating, and collecting the solid product by filtration. A total of 0.829 g (57%) of (E)-3-(5-chloro-2-tetrazol-1-yl-phenyl)-acrylic acid methyl ester was obtained. LCMS m/z 265.1 (M+H)+; 287.2 (M+Na)+. 1H NMR (CDCl3, 500 MHz) δ: 8.80 (s, 1H), 7.78 (d, J=2.2 Hz, 1H), 7.58 (dd, J=8.8, 2.2 Hz, 1H), 7.42 (d, J=8.2 Hz, 1H), 7.25 (d, J=16.0 Hz, 1H), 6.45 (d, J=16.0 Hz, 1H), 3.78 (s, 3H). To a white suspension of this ester (0.140 g, 0.529 mmol) in MeOH (3.0 mL) was added 1.0 M sodium hydroxide (1.587 ml, 1.587 mmol). The resulting suspension was stirred vigorously at rt for 2.5 h. The yellow suspension was neutralized with 1.0 N HCl (1.60 mL), and concentrated to give a beige solid. The solid was partitioned between 1.0 N HCl and EtOAc, and the layers were separated. The organic layer was washed with brine, dried over Na2SO4, filtered and concentrated to give 0.137 g (100%) of (E)-3-(5-chloro-2-tetrazol-1-yl-phenyl)-acrylic acid as a white solid. LCMS m/z 251.1 (M+H)+. 1H NMR (500 MHz, DMSO-d6) δ: 12.72 (s, 1H), 9.87 (s, 1H), 8.24 (d, J=2.2 Hz, 1H), 7.77 (dd, J=8.8, 2.2 Hz, 1H), 7.73 (d, J=8.2 Hz, 1H), 6.98 (d, J=16.0 Hz, 1H), 6.70 (d, J=16.0 Hz, 1H).
