Beilstein J. Org. Chem.2012,8, 379–389, doi:10.3762/bjoc.8.41
. Unfortunately, when applied to the synthesis of furanyl-substituted tpy 12, this method leads to irreproducible results [19]. Even turning to barium hydroxide as a base (which is known to favour Michaeladditions [20]) did not improve the course of the reaction in a substantial manner. Therefore, basic alumina
[19][21] was tested, since it is known to be an efficient promoter of aldol condensations and Michaeladditions under solvent-free conditions [22][23]. Nevertheless, the treatment of furanyl-substituted aldehydes 1, 3 and 15 did not yield the targeted diketo-intermediates, but instead the chalcones 5
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Graphical Abstract
Figure 1:
Structure and atomic numbering of 2,2’:6’,2’’-terpyridines.
Beilstein J. Org. Chem.2011,7, 1387–1406, doi:10.3762/bjoc.7.163
transformations, including aza-Michaeladditions, hydroaminations of alkynes, Buchwald–Hartwig aminations, and allylic aminations, thereby allowing the creation of several covalent bonds in a single operation. Imine derivatives are also of high synthetic value as they may act either as electrophilic or