A series of 3,3′-disubstituted and 6,6′-disubstituted BINOL derivatives was synthesized and examined in typical titanium(IV) promoted aldol reactions. The model reaction of S-ketene silyl acetal 13 and aldehydes 12a and 12b revealed that 6,6′-dibromo-BINOL derivative (R)-6 is the ligand of choice for these transformations. Up to 97% yield with excellent enantioselectivity (ee > 97%) could be achieved. Scope and limitations were demonstrated using a series of aldehydes as substrates, which were generally transformed into their aldol adducts by the (R)-6/Ti(Oi-Pr)4 catalyst with good efficacy and high enantioselectivity.
合成了一系列 3,3′-二取代和 6,6′-二取代的 BINOL 衍
生物,并在典型的
钛(IV)促进醛醇反应中进行了检验。S-ketene silyl acetal 13 与醛 12a 和 12b 的模型反应表明,6,6′-二
溴 BINOL 衍
生物 (R)-6 是这些转化反应的首选
配体。可以实现高达 97% 的产率和出色的对映选择性(ee > 97%)。以一系列醛为底物证明了该催化剂的应用范围和局限性,(R)-6/Ti(Oi-Pr)4 催化剂通常能将这些醛转化为它们的醛醇加合物,并具有良好的功效和较高的对映选择性。