Amidines constitute one of the most prolific and versatile functional groups in organic synthesis. In recent years they have become a common synthetic building block in hetero-cycle construction and the synthesis of biologically active natural products. They also have emerged as a key functional group in pharmaceutical drug design. Despite their growing biological significance, the use of amidines as bioorthogonal chemical reporters is notably absent. This is likely attributable to the central tenet in reaction design for amidine synthesis as it involves addition of an amine to an activated acyl equivalent. For example, a recent report by Chang and co-workers describes a triazole decomposition strategy resulting in an innovative three-component coupling of an alkyne, sulfonyl azide, and an amine (Scheme 1a).
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