Chelating Carboxylic Acid Amides as Robust Relay Protecting Groups of Carboxylic Acids and their Cleavage under Mild Conditions

Abstract

Free choice: Carboxamides of bispicolylamine are alternative protecting groups 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 under mild conditions to give either carboxylic acids or their methyl esters, this new protection method should find widespread application in the realm of organic synthesis.

Unusual metal complexes of N,N-bis(2-picolyl)amides – A comparative study of structure and reactivity

“…[15][16][17][18][19][20][21] In addition, the cleavage can proceed in an intramolecular fashion and give γ-, δ-and ε-lactones in moderate to high yields. [22] Figure 1: Parameters for the quantitative description of the (non-)/planarity of amides; a) twist angle τ, b) Winkler-Dunitzparameter χ N .…”

Direct Phenolysis Reactions of Unactivated Amides into Phenolic Esters Promoted by a Heterogeneous CeO2 Catalyst

“…The direct functionalization of amides is thus a highly attractive strategy in organic syntheses, where the major challenge lies in the cleavage of the amide C−N bond, which is due to the functional group interconversion arising from amidic resonance (Figure A) that renders amides poor electrophiles and unreactive toward nucleophiles. Conventionally, enzyme‐ or strong‐acid/base‐mediated C−N bond cleavage reactions of amides with alcohols generate huge amounts of undesired byproducts . Recently, catalytic C−N bond cleavage reactions, specifically the alcoholysis of amides into the corresponding esters, have received much attention and several examples have been reported .…”

Efficient Transfer of Chelating Amides into Different Types of Esters and Lactones

“…In 1970, Houghton and Puttner published a seminal work on chelating amides,1 which served us as a basis for the development of a new protection scheme for carboxylic acids 2. The approach is based on a mild conversion of a carboxamide into a methyl ester by using Cu 2+ salts in methanol.…”