Palladium-Catalyzed Direct Arylation of C–H Bond To Construct Quaternary Carbon Centers: The Synthesis of Diarylfluorene

Abstract

A novel Pd-catalyzed C-H functionalization reaction was developed to construct a quaternary carbon center with high yield. This reaction provides an efficient method for the synthesis of 9,9'-diarylfluorenes by direct arylation of monoarylfluorene.

Pure aromatic hydrocarbons with rigid and bulky substituents as bipolar hosts for blue phosphorescent OLEDs

“…Further studies demonstrated that pure aromatic hydrocarbons of anthracene 35 derivatives exhibit both electron and hole transporting properties [17][18][19] , and can be used as host emitter in OLEDs 20,21 . Due to their good conjugation and the lack of preferential moieties either for hole or for electron transport, pure aromatic hydrocarbons are expected to possess high and bipolar carrier 40 transport property, which is highly desired as host component in OLEDs, such as host for phosphors in phosphorescent OLEDs (PhOLED) [22][23][24] . During the past decades, hosts with bipolar transport ability for phosphorescent emitters have aroused great attention due to the promising device features of high 45 performance [25][26][27] and simple device structure 28 .…”

“…The geometry optimization was performed using the density functional theory (DFT) 38,39 of Gaussian 09 program under Becke's 3-parameters employing Lee-Yang-Perdew function (B3LYP) 40 with 6-31G (d*) basis set. 40 The synthetic routes for the four pure hydrocarbon molecules are described in Scheme 1 41 .All the solvents were distilled from appropriate drying agents prior to use. Commercially available reagents were used without further purification.…”

“…35 From the minor difference, it can be seen that the triplet energy of pDPFDB is the smallest, consisting with the longest molecular conjugation as discussed above. Again, in mTPFB which possesses three perihedral substitutions of 9-phenylfluorene, the triplet energy is the highest, due to the effectively blocked π- 40 conjugation originating from the increased steric hindrance [44][45][46] . High triplet energy of host is generally beneficial to blue phosphor in PhOLED.…”

“…Things are different for hole injection:35 the smallest charge distribution change (HOMO vs HOMO+h) leads to largest hole reorganization energy in pDPFDB (0.18), and the largest charge-distribution change leads to the smallest hole reorganization energy in mTPFB (0.09). Therefore, in pDPFDB, the reorganization energies of electron and hole are the40 …”

Palladium-catalysed synthesis of triaryl(heteroaryl)methanes

“…Recently, the palladium-catalysed arylation of fluorenes by the teams of Wu and Song, Xie, and Huang was reported to give diarylfluorenes (Fig. 1e)2829. Fluorene is more acidic and less sterically demanding than other diarylmethane derivatives.…”