Modification and Optimization of the Bis-picolylamide-Based Relay Protection for Carboxylic Acids to be Cleaved by Unusual Complexation with Cu<sup>2+</sup> Salts
A simple modification of our recently published protection scheme for carboxylic acids as amides resulted in a new protecting group with significantly improved properties. It requires shorter reaction times for deprotection and allows us to replace Cu(OTf)(2) by CuCl2, indicating at the same time the importance of the nature of the anion of the Cu2+ source. Since the new scheme fulfills all criteria required for an ideal protection group it should find widespread application in synthetic organic chemistry.
Efficient Transfer of Chelating Amides into Different Types of Esters and Lactones
作者:Uwe Jakob、Stephan Mundinger、Willi Bannwarth
DOI:10.1002/ejoc.201402843
日期:2014.11
corresponding esters despite the fact that the former are thermodynamically more stable. The transformations are mediated by the coordination of CuI by a chelating entity. The resulting weakening of the amide bond allows for nucleophilicattack by alcoholic hydroxyl functions. The principle is demonstrated for a wide variety of transformations, leading to different kinds of esters and lactones.
我们描述了一种将羧酸酰胺转化为其相应酯的通用方法,尽管前者在热力学上更稳定。转化是由螯合实体协调 CuI 介导的。由此产生的酰胺键弱化允许醇羟基官能团进行亲核攻击。该原理适用于各种转化,导致产生不同种类的酯和内酯。
Chelating Carboxylic Acid Amides as Robust Relay Protecting Groups of Carboxylic Acids and their Cleavage under Mild Conditions
作者:Manuel C. Bröhmer、Stephan Mundinger、Stefan Bräse、Willi Bannwarth
DOI:10.1002/anie.201100271
日期:2011.6.27
Free choice: Carboxamides of bispicolylamine are alternative protectinggroups for carboxylic acids (see scheme). As a consequence of their straightforward applicability, their high chemical stability towards a broad range of conditions, and their selective cleavage undermildconditions to give either carboxylic acids or their methyl esters, this new protection method should find widespread application