Regioselective quinazoline C2 modifications through the azide-tetrazole tautomeric equilibrium

Abstract

2-Chloro-4-sulfonylquinazolines undergo functional group swap when treated with an azide nucleophile: 1) the azide replaces the sulfonyl group at the C4 position; 2) the intrinsic azide-tetrazole tautomeric equilibrium directs the nucleofugal sulfinate from the first step to replace chloride at the C2 position. This transformation is effective with quinazolines bearing electron-rich substituents. Therefore, the title transformations are demonstrated on the 6,7-dimethoxyquinazoline core, which is present in pharmaceutically active substances. The methodology application is showcased by transforming the obtained 4-azido-6,7-dimethoxy-2-sulfonylquinazolines into the α₁-adrenoceptor blockers terazosin and prazosin by further C2-selective S_NAr reaction and azide reduction.

Keywords: 4-azido-2-sulfonylquinazolines; aromatic nucleophilic substitution; azide–tetrazole equilibrium; quinazolines; sulfonyl group dance.