Solid-Phase Synthesis of Urea and Amide Libraries Using the T2 Triazene Linker

Abstract

Starting from Merrifield resin, primary amines were immobilized in two steps by triazene linkage (T2-linker). While reaction with isocyanates gave rise to resin-bound urea derivatives, acylation by acid chlorides or anhydrides furnished amides bound to solid support via the nitrogen atom, therefore representing a novel backbone amide linker. Cleavage from the resin was conducted using dilute trimethylsilyl chloride or trifluoroacetic acid, respectively, to yield ureas and amines/amides in a library format (altogether 60 examples; manual synthesis: 17 ureas, 6 mono-alkylated ureas [including dihydroxylation and ozonolysis/Wittig reaction]; automated synthesis: 15 ureas, 15 amides) in high purities and good overall yields. The synthesis of a small library (4 x 4 member) was successfully conducted on a Bohdan Neptune synthesizer.