High Yield, Low-Waste Synthesis of a Family of Pyridyl and Imidazolyl-Substituted Schiff Base Linker Ligands

Solid-state synthesis (S3) is an attractive approach to organic synthesis as in principle it offers minimal solvent waste and high yield. However, many functional groups are ill-suited for S3 reactions, which tend to only proceed when substrates are aligned in the solid-state according to the topochemical principle. The aim of this work is to use high yield, low-waste synthetic methods to develop a library of novel Schiff bases that can be utilized as linker ligands to prepare coordination networks. Herein, we report that eight pyridyl- and/or imidazolyl-substituted Schiff bases, 1–8, five of which are new chemical entities, can be prepared via reaction of an amine and an aldehyde without the use of solvent. All eight compounds were prepared via solvent-drop grinding (SDG) in multigram scale in >95% yield and each was characterized by FTIR, 1H and 13C NMR spectroscopies and single crystal X-ray diffraction. One of the aldehydes used is a liquid under ambient conditions so its reactions to form 1–4 are not...