Piperazine Amide Linker for Cyclative Cleavage from Solid Support: Traceless Synthesis of Dihydroquinoxalin-2-ones

A piperazine amide linker for cyclative cleavage from solid support and its use in the traceless solid-phase synthesis of dihydroquinoxalinones are described. Piperazine was attached to Wang resin via a carbamate linkage and acylated with Fmoc-amino acids. Following Fmoc group removal, resin-bound amines were reacted with 1-fluoro-2-nitrobenzenes. The nitro group of the resulting 2-nitroanilines was reduced, and acyclic precursors, in contrast to traditional ester-type linkage, remained attached to the resin. Target dihydroquinoxalinones were obtained either by acid- or microwave-mediated cyclative cleavage. The synthesis provided crude compounds of high purity and enabled the preparation of stable immobilized linear intermediates. The linker is suitable for combinatorial synthesis of compound libraries.