Orientation effects on C2(5)-C2′(5′) linked bioxazole isomers synthesized via regioselective and sequential C-H arylation

Bis(4-fluorophenyl) substituted oxazole (2,5-Oxz) and C2(5)-C2'(5') linked bioxazole isomers (C2-C2'_BOxz, C2-C5'_BOxz and C5-C5'_BOxz) were concisely synthesized via palladium-catalyzed regioselective and sequential C-H arylation in 1-3 reaction steps along with 20%-83% of total yields from oxazole and 4-bromofluorobenzene. The linking orientation plays a key role in the packing geo metry and photophysical properties of C2-C2'_BOxz, C2-C5-_BOxz and C5-C5'_BOxz. These bioxazole isomers in solid state showed significant differences in photoluminescence quantum yields (PLQY) (0.33, 0.25 and 0.04, respectively), delayed fluorescence properties and powder X-ray diffraction (PXRD) patterns, suggesting the divergence in intermolecular interactions. The theoretically calculated gradient isosurfaces and complexation energies indicate the existence of intense pi-pi interactions between molecular layers, which are in good agreement with the variation trend of optical properties. (C) 2020 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.