Naked-Eye Bead Property Estimation Using a Red Safety-Catch Linker

Abstract

The attachment of linker molecules to polymer beads used as insoluble supports for organic synthesis is a frequent requirement. Defined immobilization of these linker molecules before loading selected building blocks is crucial for subsequent transformations. Therefore, the control of the linker attachment is a central task. Because the molecular bodies of linkers are not incorporated in the final molecules, they can often be replaced or modified without affecting the structure of the products that are finally released. Consequently, it seems straightforward to look for coloured substitutes to established linker molecules. By using coloured linkers, visual inspection of the beads enables fast property estimation after attachment and monitoring of losses during synthesis. This very simple estimation does not have a validated loading determination, but is a useful element of straightforward and non-destructive reaction control that has general applicability. Here we present a red azo dye as an alternative to the Kenner safety-catch linker.