Iodine → 2-Amino-3-(6-bromo-2H-pyrazolo[4,3-b]pyridin-2-yl)-2-methylpropionitrile

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Reaction Steps

2-Amino-3-(6-bromo-2H-pyrazolo[4,3-b]pyridin-2-yl)-2-methylpropionitrile (416 mg, 80%) was prepared using a procedure similar to that described in Example 1, part b, except starting from 1-(6-bromo-2H-pyrazolo[4,3-b]pyridin-2-yl)propan-2-one (471 mg). 1-(6-Bromo-2H-pyrazolo[4,3-b]pyridin-2-yl)propan-2-one was prepared using a procedure similar to that described in Example 105 part c and d except starting from 2-[2-(tert-butyldimethylsilanyloxy)propyl]-6-bromo-2H-pyrazolo[4,3-b]pyridine (289 mg, 39%) that was prepared using a procedure similar to that described in Example 155 except starting from 5-bromo-3-nitropyridine-2-carboxaldehyde (462 mg). 5-Bromo-3-nitropyridine-2-carboxaldehyde was prepared using a procedure similar to that described in Example 136 part a to c except starting from 2-amino-5-bromo-3-nitropyridine (50 g) and using iodine (69.9 g) in part a instead of copper bromide to generate 5-bromo-2-iodo-3-nitropyridine as a yellow solid (27.4 g, 36%). Oxidative cleavage using a 4% solution of osmium tetroxide in water (4 mL) and sodium periodate (6.7 g) was carried out in a mixture of THF and water (10:1, 390 mL) in part c instead of ozonolysis following a procedure similar to that described in Example 61 to afford 5-bromo-3-nitropyridine-2-carboxaldehyde as a tan solid (3.8 g, 62%) from 5-bromo-3-nitro-2-vinylpyridine (6 g).

Provenance & Evidence