Sulfonyl Group Dance: A Tool for the Synthesis of 6‑Azido-2-sulfonylpurine Derivatives

9-Substituted 2-chloro-6-sulfonylpurines
provide 6-azido-2-sulfonylpurine
derivatives with 61–83% yields when treated with sodium azide.
Under optimized reaction conditions, the title compounds are obtained
in a one-pot process, which involves a sequential treatment of 2,6-dichloropurines
with a selected sodium sulfinate and sodium azide. Such a sulfonyl
group dance (functional group swap) results from a cascade of SNAr reactions, which are facilitated by azidoazomethine-tetrazole
(azide-tetrazole) tautomeric equilibrium. The formation of Meisenheimer-type
intermediates as tetrazolopurine tautomers was supported by various
spectroscopic methods, including 15N NMR.