“One-Pot” In Situ Tandem Reaction─Dy(III) Coordination-Catalyzed Multicomponent Condensation of Salicylaldehyde Derivatives to Obtain Ketals

Abstract

It is difficult to subject simple reaction starting materials to a “one-pot” in situ tandem reaction without post-treatment under mild reaction conditions to obtain multimers with complex structural linkages. In organic synthesis, acetal reactions are often used to protect derivatives containing carbonyl functional groups. Therefore, acetal products tend to have very low stability, and performing multi-step condensation to obtain complex multimeric products is difficult. Herein, we achieved the first efficient multiple condensation of o-vanillin derivatives using Dy(OAc)3·6H2O undergoing a “one-pot” in situ tandem reaction under mild solvothermal conditions to obtain a series of dimers (I and II, clusters 1 and 2) and trimers (I and II, clusters 3 and 4). When methanol or ethanol is used as the solvent, the alcoholic solvent participates in acetal and dehydration reactions to obtain dimers (I and II). Surprisingly, when using acetonitrile as the reaction solvent, the o-vanillin derivatives undergo acetal and dehydration reactions to obtain trimers (I and II). In addition, clusters 1–4 all showed distinct single-molecule magnetic behaviors under zero-field conditions. To the best of our knowledge, this is the first time that multiple acetal reactions catalyzed by coordination-directed catalysis under “one-pot” conditions have been realized, opening a new horizon for the development of fast, facile, green, and efficient synthetic methods for complex compounds.

Aggregation-Induced Emission via the Restriction of the Intramolecular Vibration Mechanism of Pinacol Lanthanide Complexes

“…Recently, coordination-driven in situ tandem reactions have attracted extensive research attention owing to their facile synthetic procedures, high reaction yields, and high atom utilization. After the metal ions participate in the coordination, multistep catalytic organic reactions occur to form complex organic ligands that are difficult to achieve using traditional one-step organic synthesis procedures. − Although some progress has been made, further research is still required to gain a deeper understanding of these in situ coordination-catalyzed tandem reactions to establish specific rules to guide their precise control. − Owing to its rapid detection ability, high precision, and simple operation, HRESI-MS has become the tool of choice to explore complex tandem reactions under one-pot conditions. − To deeply explore the pinacol ligands in the PyraLn structure, the pinacol coupling reaction, i.e., the McMurry coupling reaction, of 2-pyrazinecarbaldehyde assisted by the Ln­(III) ion was conducted (Figure S6). After the reaction process was experienced for 24 h, the reaction solution was subjected to an electron paramagnetic resonance (EPR) test, and the experimental results showed that obvious signal peaks were detected, which proved the formation of a free radical coupling process in the reaction solution (Figure S7).…”