[摘要]：A series of 9,10-diarylanthracenes with various substituents at the ortho positions have been synthesized by palladium-catalyzed cross-coupling reactions. Such compds. exhibit interesting phys. properties and can be applied as mol. switches. Despite the high steric demand of the substituents, products were formed in moderate-to-good yields. In some cases, microwave conditions further improved yields. Bis-coupling afforded two isomers (syn and anti) that do not interconvert at room temp. These products were easily sepd. and their relative stereochemistries were unequivocally assigned by NMR spectroscopy and X-ray anal. The syn and anti isomers exhibit different phys. properties (e.g., m.ps. and solubilities) and interconversion by rotation around the aryl-aryl axis commences at <100癈 for fluoro-substituted diarylanthracenes and at >300癈 for alkyl- or alkoxy-substituted diaryl-anthracenes. The reactions with singlet oxygen were studied sep. and revealed different reactivities and reaction pathways. The yields and reactivities depend on the size and electronic nature of the substituents. The anti isomers form the same 9,10-endoperoxides as the syn species, occasionally accompanied by unexpected 1,4-endoperoxides as byproducts. Thermolysis of the endoperoxides exclusively yielded the syn isomers. The interesting rotation around the aryl-aryl axis allows the application of 9,10-diarylanthracenes as mol. switches, which are triggered by light and air under mild conditions. Finally, the oxygenation and thermolysis sequence provides a simple, synthetic access to a single stereoisomer (syn) from an unselective coupling step.
