Sterically Shielded Titanocene Enolates – Synthesis, Structure and Their Exceptional Stability towards Hydrolysis
作者:Michael Schmittel、Rolf Söllner、Helmut Werner、Olaf Gevert
DOI:10.1002/cber.19971300209
日期:1997.2
various sterically congested sodium enolates, generated by quantitative deprotonation of stable enols (of diphenylacetaldehyde in the case of 5), with dichlorotitanocene afforded a series of novel titanium enolates 1-5. The crystal structure of 1 could be determined. Due to the considerable steric shielding of the β,β-diaryl moiety, all the titanium enolates exhibit an oustanding stability towards hydrolysis
由稳定的烯醇(在5的情况下,二苯乙醛的定量)质子化所引起的各种空间拥塞的烯醇钠与二氯噻吩并茂的反应,提供了一系列新型的烯醇钛1-5。可以确定1的晶体结构。由于β,β-二芳基部分的相当大的空间屏蔽作用,所有的烯醇钛盐都表现出极好的水解稳定性,随着对CC双键的取代基的更高空间需求,该稳定性增加。通过UV光谱法研究了水解的动力学,其在THF /水(1:1)和乙腈/水(1:1)中为拟一级反应。在这些溶剂混合物中测得的拟一级反应速率常数在6.4·10的范围内-4 s -1 < k 1 <1.1·10 -3 s -1。为了进行比较,应该表现出通常的烯醇钛酸酯对水解敏感性的6的水解快约1000倍。