Synthesis of 2-Substituted Pyridines via a Regiospecific Alkylation, Alkynylation, and Arylation of Pyridine <i>N</i>-Oxides
作者:Hans Andersson、Fredrik Almqvist、Roger Olsson
DOI:10.1021/ol070184n
日期:2007.3.1
Grignard reagents to pyridine N-oxides in THF at room temperature followed by treatment with acetic anhydride at 120 degrees C afforded 2-substitutedpyridines in good to high yields. Furthermore, by exchanging acetic anhydride for DMF in the second step, 2-substitutedpyridine N-oxides were obtained, as intermediates suitable for addition of a second Grignard reagent for the synthesis of 2,6-disubstituted
Addition of Grignard reagents to pyridine N-oxides in THF at low temperature (-78 to -20 degrees C) and treatment with TFAA provides an efficient general procedure for synthesis of substitutedpyridines. The method is compatible with a range of functional groups such as esters, halogens and nitriles.
Synthesis of substituted 4-benzyloxypyridinium salts by the addition of Grignard reagents to pyridine N-oxides provides an efficient route for obtaining substituted 4-pyridones or 4-aminopyridinium salts.