Titanium enolates and “ate” complexes of N,N-disubstituted amides and thioamides in the Michael reaction.
作者:Lilia Z. Viteva、Tzveta S. Gospodova、Yuri N. Stefanovsky
DOI:10.1016/s0040-4020(01)85243-1
日期:1994.1
The synthetic potential, regio- and stereoselectivity of titanium dialkylamide and dialkylthioamide enolates and “ate” complexes in reaction with some conjugate carbonyl compounds are investigated. Titanium enolates react preferentially in 1,2-position while “ate” complexes afford 1,4-regiocontrol. The stereochemical behaviour of the latter follows in general the lithium and potassium precursors. Marked
研究了二烷基酰胺钛和二烷基硫酰胺钛烯酸酯和“酸酯”配合物与某些共轭羰基化合物反应的合成潜力,区域和立体选择性。烯醇钛酸酯优先在1,2-位发生反应,而“盐”配合物则提供1,4-区域控制。后者的立体化学行为通常遵循锂和钾前体。用酰胺发现了溶剂和亲电试剂几何形状对1,4-立体选择性的显着影响,而对硫代类似物却没有。酰胺钛“酸盐”配合物的立体化学与环状过渡态相关。溶剂效应通过参与过渡结构来解释。讨论了钛“盐”配合物的一些优点。