Сообщение
pirazol » Пн апр 03, 2017 10:51 pm
Вот ещё методика с тетраэдрона;
C. D. Gabbutt et al. / Tetrahedron 62 (2006) 737–745;
A solution sodium nitrite (7.05 g, 102 mmol) in water (15 mL) was added slowly to a cold (0 8C) stirred solution of 2-amino-4-chlorobenzoic acid (17.16 g, 100 mmol) in water (250 mL) and concd HCl (75 mL). On completion of the addition the solution was stirred for 5 min and then a solution of the appropriate halide (102 mmol) in water (25 mL) was added. The cooling bath was removed and the mixture stirred for a further 5 min before carefully heating the suspension to 90 8C for 10 min. The mixture was cooled to room temperature and the precipitated solid collected and washed with water (3!50 mL). The crude product was recrystallised from ethanol and water. The following acids were prepared in this way:
4-Chloro-2-iodobenzoic acid 7a. From potassium iodide as a light brown powder (16.9 g, 60%), mp 160–163 8C (lit. mp 165–166 8C25), dH 3.49 (1H, br s, OH), 7.63 (1H, dd, JZ8.4, 2.1 Hz, 5-H), 7.80 (1H, d, JZ8.3 Hz, 6-H), 8.14 (1H, d, JZ2.1 Hz, 3-H).
2-Bromo-4-chlorobenzoic acid 7b. From copper(I) bromide as a light brown powder (14.4 g, 61%), mp 154–156 8C (lit. mp 155 8C26), dH 3.84 (1H, br s, OH), 7.46 (1H, dd, JZ8.3, 2.1 Hz, 5-H), 7.65 (1H, d, JZ2.0 Hz, 3-H), 7.76 (1H, d, JZ8.4 Hz, 6-H).
