Expeditious Solid‐Phase Synthesis of Pyrazoledicarboxylic Acid Derivatives by Functionalization of Resin‐Bound Cyanoformate

Abstract

Esterification of the Wang resin 5 with the monoamide of oxalic acid (oxamic acid, 7) followed by dehydration of the amide function furnishes the resin-bound cyanoformate 9, which can be elaborated by zinc-catalyzed reaction with β-keto esters. The obtained enamino keto diesters 10a-d react with hydrazines affording, after removal from the solid sup-

Solid-Phase Synthesis of Amino Acid Derived N-Unsubstituted Pyrazoles via Sydnones

“…Solid-phase synthesis of heterocycles and 1,3-dipolar cycloadditions on solid supports have recently been reviewed . Solid-phase synthesis of pyrazoles has been studied mainly via hydrazine reactions and also via 1,3-dipolar cycloadditions . Acid-cleavable 2-methoxy-substituted resin has proven very useful in traceless solid-phase synthesis, and it has been utilized, e.g., in the synthesis of five-membered nitrogen heterocycles such as imidazoles, 1,2,4-triazoles, and 1,2,3-triazoles .…”