Various lanthanide shift reagents Ln(fod)3 were found to affect the conformational composition of 2-methoxychalcones. Coordination of Yb(fod)3 occurs mainly at the carbonyl oxygen atom of the substrate, while Eu(fod)3 and shift reagents derived from other lanthanides coordinate substituted chalcones as bidentate ligands, giving rise to a secondary tetrachelate with the corresponding change of conformation of the substrate molecule. The possibility for chelation is determined by steric hindrances in the vicinity of the substrate coordination centers and concurrent coordination of other electron-donor groups present in the substrate molecule.
各种
镧系位移试剂Ln(fod)3被发现会影响2-甲氧基
查耳酮的构象组成。
镱(fod)3主要在底物的羰基氧原子上发生配位,而
铕(fod)3及其他
镧系衍生的位移试剂则以双齿
配体形式配位取代的
查耳酮,导致形成次级四齿螯合物,伴随底物分子构象的相应变化。是否能形成螯合取决于底物配位中心附近的位阻以及底物分子中存在的其他电子供体基团的协同配位。