ChemInform Abstract: New Syntheses of Substituted Pyridines via Bromine—Magnesium Exchange.
Abstract
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ChemInform Abstract
Various functionalized pyridines are obtained from bromopyridines by treatment with iPrMgCl at room temperature followed by reaction of the intermediate pyridine Grignard reagent with electrophiles. Single bromine—magnesium exchange reactions take place on 2,6-, 3,5-, 2,3-, 2,5-, and 3,4-dibromopyridines affording the corresponding bromopyridines, which can be used for a second exchange step to provide difunctionalized pyridines. The reaction of 2,3- and 2,5-dibromopyridines proceeds with complete regioselectivity whereas the 3,4-dibromo derivative gives a mixture of regioisomers. The bromine—magnesium exchange is successfully applied to the synthesis of 4-azaxanthone.
