827614-64-2

2-Aminopyridine-5-boronic acid, pinacol ester can be used in a microwave-assisted, four-component coupling process leading to amino substituted imidazopyridines.

General procedure for the synthesis of 2-aminopyridine-5-boronic acid pinacol ester from 2-amino-5-bromopyridine and biboronic acid pinacol ester: a 5L three-necked flask was assembled with a mechanical stirrer, and 300 g of 2-amino-5-bromopyridine, 528 g of biboronic acid pinacol ester, 3 L of 1,4-dioxane, 42.4 g of [Pd(dppf)2Cl2], and 593 g of anhydrous potassium acetate were added to it. . The reaction system was displaced three times with nitrogen to remove air, followed by heating to 80 °C and stirring the reaction for 16 hours. The progress of the reaction was monitored by TLC and after confirming the completion of the reaction, it was cooled to room temperature and diafiltrated. The filter cake was washed twice with 200 mL of dichloromethane, the filtrates were combined and concentrated to dryness. To the residue, 2 L of methanol was added and stirred at 37 °C overnight. Subsequently, 200 g of activated charcoal was added, stirred at room temperature and filtered. The filtrate was concentrated to dryness to obtain an oil. To the oily substance was added 150 mL of petroleum ether and 2 L of methyl tert-butyl ether (MTBE), pulsed overnight and filtered to give 380 g of 2-aminopyridine-5-boronic acid pinacol ester in 99% yield.

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