Synthesis of novel halopyridinylboronic acids and esters. Part 3: 2, or 3-Halopyridin-4-yl-boronic acids and esters

This paper describes a general method for the synthesis and the isolation of novel 2, or 3-halopyridin-4-yl-boronic acids and esters , . These compounds are prepared taking in account a regioselective halogen–metal exchange using nBuLi or directed ortho-metalation using LDA and subsequent quenching with triisopropylborate starting from appropriate mono or dihalopyridines. All substrates studied to date provided a single regioisomeric boronic acid or ester product. Additionally, these compounds have been found to undergo Pd-catalysed coupling with a range of arylhalides and authorise a strategy to produce new pyridines libraries.