Advantages of Asymmetry: A Synthetic and Structural Exploration of s-Triazine Chemistry Starting From Pyrrolated Ammeline and Melam.

Melam and ammeline are simple, s-triazine-based compounds first described by Liebig nearly 200 years ago. Outgoing from these two compounds, synthetic strategies for asymmetrically substituted s-triazines were developed. As the initial key step, Clauson-Kaas pyrrolation of the compounds' primary amino groups was carried out, significantly improving their solubility in organic solvents and thereby facilitating further conversions. These include functionalization of the s-triazine bridging amino group of pyrrolated melam by reaction with electrophiles, while pyrrolated ammeline was deoxychlorinated and subsequently reacted with nucleophiles to displace the resulting Cl substituent. Moreover, a reaction protocol for reversion of pyrrolyl into amino groups was developed, which involved ozonolysis, followed by treatment with aqueous NaOCl of the resulting formamide derivatives. Thereby, melam derivatives with essentially the same coordination site but enhanced solubilities were obtained. This enabled the preparation of a Cu(II) coordination complex from aqueous solution, which is unheard of for melam itself. Finally, the thus accessible s-triazines were structurally characterized to gain deeper insights on how the different conducted transformations influence the physicochemical properties relevant for future applications.