Solid‐Phase N‐Electrophilic Amination of 2‐Aminopyridines: Preparation of 2‐Substituted‐[1,2,4]triazolo[1,5‐a]pyridine Derivatives

Solid‐phase N ‐amination of 2‐aminopyridin‐3/5‐yl derivatives supported via an acid labile linker by hydroxylamine‐based electrophilic NH 2 + equivalents is described. A comparison of aminating efficiency and stability between O ‐Mesitylenesulfonyl Hydroxylamine (MSH) ( 5 ) and O ‐(2,4‐Dinitrophenyl)hydroxylamine (Dnp‐ONH 2 ) ( 8 ) on solid‐phase is also reported. A practical two‐step preparation of 2‐substituted‐[1,2,4]triazolo[1,5‐ a ]pyridin‐6/8‐yl derivatives ( 4 ) on solid‐phase using this methodology gave compounds in good purity and yields.