Solid-Phase Synthesis of Libraries of Triazine Dendrimers and Orthogonal Staining Methods for Tracking Reactions on Resin

Reaction tracking is important in solid-phase synthesis, especially for the preparation of dendrimers. In this study, a pair of orthogonal staining methods involving ninhydrin and Alizarin R was used to monitor the presence of alkyl amines or aryl chlorides, respectively, for tracking a reaction's progress. This staining method was applied to the solid-phase dendrimer synthesis of a small library of triazine dendrimers that varied in generation from 1 to 3 and with specific ratios of surface groups. Starting with a Rink amide resin, iterative reactions of cyanuric chloride and a linking diamine, aminomethylpiperidine, provided the desired materials. Peripheral dichlorotriazines could be reacted selectively with two different amine nucleophiles to yield a multifunctional surface in a total yield of 81–87 %. The whole preparation process could be accomplished within one week, which dramatically improved the preparation efficiency.