Chelidamic Acid Derivatives: Precursors To Functionalized Pyridyl Cryptands & Functionalized Metal Ligands

Pyridyl cryptands, such as 12-16 formed from pyridine-2,6-dicarbonyl chloride (4) and crown ether diols 7-11, have been demonstrated to be excellent hosts for viologens (N,N'-dialkyl-4,4'-bipyridinium salts, 2) with K-a values of similar to 10(4) to 10(6) M-1 and thus are considered to be ideal building blocks for supramolecular systems. However, in order to incorporate these host motifs into useful starting materials, functionalization is required; in this article we describe syntheses of 23 new chelidamic acid (2,6-dicarboxy-4-hydroxypyridine, 5) derivatives that can be used to prepare functional pyridyl cryptands and functional metal ligands. The preparation and characterization of three new functionalized pyridyl cryptands are also included. (C) 2021 Elsevier Ltd. All rights reserved.