Substituted pyridines

Abstract

A class of 2,4-; 2,3,4-; 2,4,6-; 2,3,4,5,6-substituted pyridines is provided which include novel compounds. The substitutions are achieved according to methods disclosed herein in which a metallated pyridine is reacted with an electrophile. Suitable electrophiles include CO, SO, dialkylcarbonates, ureas, formamides, amides, carboxylic acid esters, mono- and dihaloalkyls, halogens such as chlorine, fluorine, bromine, and iodine, metallic salts, sulfones, sulfonyls, aldehydes, ketones, anhydrides, nitriles, and electrophilic boron compounds including, but not limited to, boron trialkoxides and boron trihalides. The subject invention more specifically discloses a process for the synthesis of 2,6-difluoropyridin-4-ylboronic acid which comprises: (1) reacting 2,4,6-trifluoropyridine with hydrazine monohydrate to produce 2,6-difluoro-4-hydrazinopyridine, (2) reacting the 2,6-difluoro-4-hydrazinopyridine with elemental bromine to produce 4-bromo-2,6-difluoropyridine, and (3) reacting the 4-bromo-2,6-difluoropyridine with an organolithium compound and a borate at a temperature of less than 0° C. to produce the 2,6-difluoropyridin-4-ylboronic acid, wherein said process is conducted in an organic solvent.