Functionalised pyridyl- and pyrimidyl-boronic acids and derived new biheteroaryls
The novel substituted pyridylboronic acids 2-ethoxy-3-pyridylboronic acid 103, 2,6- dimethoxy-3-pyridylboronic acid 146, 2,3-dimethoxy-4-pyridylboronic acid 158, 2,6- difluoro-3-pyridylboronic acid 225, 2,6-dichloro-3-pyridylboronic acid 230 and 2,3- dichloro-4-pyridylboronic acid 238 have been synthesised, and the synthesis of existing alkoxy pyridylboronic acids 2-methoxy-5-pyridylboronic acid 40 and 2-methoxy-3- pyridylboronic acid 43 has been optimized and scaled up. The novel substituted pyrimidylboronic acids 2-chloro-5-pyrimidylboronic acid 244 and 2-amino-5- pyrimidylboronic acid 221 have been synthesised. All of the above mentioned boronic acids were shown to undergo palladium-catalysed Suzuki cross-coupling reactions with a variety of heteroaryl halides to yield novel heteroarylpyridine derivatives. A range of halogenated aromatics and heteroammatics bearing primary amine groups have been shown to be suitable substrates for Suzuki-Miyaura cross-coupling reactions with arylboronic acids and pyridylboronic acids under standard conditions, without the need for protection/deprotection steps. New amino-SLibstituted arylpyridines, bipyridines, pyrazinopyridines, indolinopyridines, carbazolopyridines and indolopyridines have thereby been obtained. One derivative was further functionalised via diazotisation.