Synthesis of Structurally Diverse Emissive Molecular Rotors with Four-Component Ugi Stators

The use of the multicomponent Ugi reaction to rapidly prepare a library of dumbbell-like molecular rotors is highlighted here. The synthetic strategy consisted of the atom-economic access to 15 bulky and structurally diverse iodinated stators, which were cross-coupled to the 1,4-diethynylphenylene rotator. From those experiments, up to six rotors 1a–c and 1l–n were obtained, with yields ranging from 35 to 69% per coupled C–C bond. In addition to the framework diversity, five of these compounds showed aggregate-enhanced emission properties thanks to their conjugated 1,4-bis­(phenylethynyl)­benzene cores, a property that rises by increasing the water fraction (f w) in their THF solutions. The results highlight the significance of the diversity-oriented synthesis of rapid access to new molecular fluorescent rotors.